Piezoelectric valve system

ABSTRACT

A valve system having a valve operated by a piezoelectric device to control the flow of fluid through the valve system. Movement of the valve is controlled by a pre-stressed bender actuator that changes its shape by deforming in opposite axial directions in response to a control signal applied by an actuator control system. The valve system may comprise a common rail fuel injector, electrohydraulic actuator system, electronically-controlled fuel injector, gasoline port injector, fluid metering valve, relief valve, reducing valve, direct valve or direct-injection gasoline injector.

TECHNICAL FIELD

[0001] The present invention relates generally to valve systems forcontrolling a flow of fluid through a fluid passageway and, moreparticularly, to a valve system having a valve actuated by apiezoelectric device to control the flow of fluid through the valvesystem.

BACKGROUND

[0002] Valve systems have been designed in the past having a valveactuated by a solenoid, piezoelectric stack or magnetorestrictive rod tocontrol the flow of fluid through the valve system. The valve system maycomprise a common rail fuel injector, electrohydraulic actuator system,electronically-controlled fuel injector, gasoline port injector, fluidmetering valve, relief valve, reducing valve, direct valve ordirect-injection gasoline injector by way of example.

[0003] However, in solenoid-controlled valve systems, it is oftendifficult to accurately control movement and positioning of the valvethrough the control signals applied to the solenoids. This is especiallytrue when intermediate positioning of a solenoid-controlled valvebetween two opposite, fixed positions is desired. Solenoid-controlledvalves, by their very nature, are susceptible to variability in theiroperation due to inductive delays, eddy currents, spring preloads,solenoid force characteristics and varying fluid flow forces. Each ofthese factors must be considered and accounted for in asolenoid-controlled valve system design. Moreover, the response time ofsolenoids limits the minimum possible dwell times between valveactuations and makes the valve system generally more susceptible tovarious sources of variability.

[0004] While solenoids provide large forces and have long strokes,solenoids do have certain drawbacks. For example, first, duringactuation, current must be continuously supplied to the solenoid inorder to maintain the solenoid in its energized position. Further, toovercome the inertia of the armature and provide faster response times,a solenoid is driven by a stepped current waveform. A very large currentis initially provided to switch the solenoid; and after the solenoid haschanged state, the drive current is stepped down to a minimum valuerequired to hold the solenoid in that state. Thus, a relatively complexand high power current driver is required.

[0005] In addition to requiring a relatively complex and high currentpower source, the requirement of continuous current flow to maintain thesolenoid at its energized position leads to heating of the solenoid. Theexistence of such a heat source, as well as the ability to properlydissipate the heat, is often of concern depending on the environment inwhich the solenoid is used.

[0006] Additionally, the force produced by a solenoid is dependent onthe air gap between the armature and stator and is not easily controlledby the input signal. This makes the solenoid difficult to use as aproportional actuator. Large proportional solenoids are common, but theyoperate near or at the saturation point and are very inefficient. Small,relatively fast acting non-proportional solenoids may have responsetimes defined by the armature displacement as fast as 350 microseconds.However, this response time can be a significant limitation in someapplications that require high repetition valve actuation rates orclosely spaced events. Further, it is known that there is a substantialdelay between the start of the current signal and the start of thearmature motion. This is due to the inductive delay between the voltageand magnetic flux required to exert force on the armature. In valvesystems, such delays lead to variability.

[0007] Electroactive actuators such as piezoelectric stacks andmagnetorestrictive rods eliminate the response time and proportionalityshortcomings of the solenoid. The piezoelectric stacks, due to theircapacitive behavior, offer the benefit of drawing no power during “holdin”, where actuation is maintained for a long period of time. However,these actuators have shortcomings of their own. Piezoelectric stacks andmagnetorestrictive actuators possess impressive force, but have verysmall stoke capabilities. The output of these actuators must then bemechanically or hydraulically amplified, limiting the response time andproportionality benefits that they offer. Because of their small straincapabilities, these actuators also tend to be large. Additionally, theseactuators are unidirectional, i.e., they move in only one direction inresponse to a control signal. Therefore, any valve or mass moved by theactuator requires a return biasing force, such as by a return spring, tobe applied to return the valve or mass to its original position. Often,the spring comprises a significant amount of the force required to movethe valve or mass and represents another source of variability. Also,the beneficial response time of the actuator will have no impact on thereturn of the valve or mass, as it depends completely on the returnspring.

[0008] Thus, the present invention is directed to overcoming one or moreof the problems set forth above.

SUMMARY OF THE INVENTION

[0009] While the invention is described in connection with certainembodiments, it will be understood that the invention is not limited tothese embodiments. On the contrary, the invention includes allalternatives, modifications and equivalents as may be included withinthe spirit and scope of the present invention.

[0010] In accordance with one embodiment of the present invention, avalve system, such as a common rail fuel injector by way of example,includes a valve body and a fluid chamber disposed within the valvebody. The fluid chamber is adapted to communicate with a fluid sourcefor containing fluid therein. A fluid orifice communicates with thefluid chamber. A valve member mounted within the valve body is movablebetween a closed position for closing the fluid orifice and an openposition for opening the fluid orifice. A pre-stressed bender actuatoroperatively engages the valve member and is operable to selectively movethe valve member to at least one of the closed and open positions toclose and open the fluid orifice.

[0011] In accordance with another embodiment of the present invention, avalve system, such as a common rail fuel injector by way of example,includes a valve body and a fluid chamber disposed within the valvebody. The fluid chamber is adapted to communicate with a fluid sourcefor containing fluid therein. A fluid orifice communicates with thefluid chamber. A control fluid chamber is disposed within the valve bodyand is adapted to communicate with a fluid source for containing fluidtherein. The control fluid chamber is also adapted to selectivelycommunicate with a drain for draining fluid from the control fluidchamber. A valve member is mounted within the valve body and is movablebetween a closed position for closing the fluid orifice and an openposition for opening the fluid orifice. The valve member moves betweenthe open and close positions in response to a difference in fluidpressure in the fluid chamber and in the control fluid chamber. Acontrol valve member is mounted within the valve body and is operable tomove between a closed position for containing fluid within the controlfluid chamber and an open position for draining fluid from the controlfluid chamber. A pre-stressed bender actuator operatively engages thecontrol valve member and is operable to selectively move the controlvalve member to at least one of the closed and open positions.

[0012] In accordance with yet another embodiment of the presentinvention, an apparatus is provided for adjusting a preload of apiezoelectric device having first and second opposed surfaces and aperipheral edge extending therebetween. The apparatus includes aclamping device configured to engage the first and second opposedsurfaces of the piezoelectric device proximate the peripheral edgethereof. The clamping device is operable to apply a variable clampingforce to the piezoelectric device. A load device operatively engages theclamping device and is operable to vary the applied clamping force toadjust the preload of the piezoelectric device.

[0013] In accordance with still yet another embodiment of the presentinvention, a valve system, such as a gasoline port injector ordirect-injection gasoline injector by way of example, includes a valvebody having a fluid inlet adapted to communicate with a fluid source anda fluid outlet adapted to emit fluid. A fluid passageway extends throughthe valve body between the fluid inlet and the fluid outlet. A valvemember is mounted at least partially in the fluid passageway and ismovable between a closed position for closing the fluid orifice and anopen position for opening the fluid orifice. A pre-stressed benderactuator operatively engages the valve member and is operable toselectively move the valve member to at least one of the closed and openpositions to close and open the fluid orifice.

[0014] In accordance with another alternative embodiment of the presentinvention, a fluid metering valve includes a fluid reservoir chamberadapted to communicate with a fluid source for containing fluid therein.A fluid outlet communicates with the fluid reservoir chamber. A plungermember is mounted for selective movement in the fluid reservoir chamberand is operable to meter a volume of fluid from the fluid orifice uponmovement of the plunger member toward the fluid outlet. A pre-stressedbender actuator operatively engages the plunger member and is operableto selectively move the plunger member toward the fluid outlet to meterthe volume of fluid from the fluid orifice.

[0015] In accordance with still yet another embodiment of the presentinvention, a fluid metering valve includes a fluid reservoir chamberadapted to communicate with a fluid source for containing fluid therein.A fluid outlet communicates with the fluid reservoir chamber. Apre-stressed bender actuator is operable to act directly on the fluidcontained in the fluid reservoir chamber so that a volume of fluid ismetered from the fluid outlet upon actuation of the bender actuatortoward the fluid outlet.

[0016] In accordance with still yet another embodiment of the presentinvention, a fluid metering valve includes an inlet fluid passageadapted to communicate with a fluid source for carrying fluid therein.An outlet fluid passage communicates with the inlet fluid passage. Avalve seat is disposed at a juncture of the inlet fluid passage and theoutlet fluid passage. A valve member is mounted for selective movementrelative to the valve seat between a closed position for closing fluidcommunication between the inlet fluid passage and the outlet fluidpassage and an open position for opening fluid communication between thefluid inlet passage and the fluid outlet passage to meter a volume offluid through the outlet fluid passage. A pre-stressed bender actuatoroperatively engages the valve member and is operable to selectively movethe valve member to at least one of the open and closed positions.

[0017] In accordance with yet another alternative embodiment of thepresent invention, a fluid metering valve includes an inlet fluidpassage adapted to communicate with a pressurized fluid source forcarrying pressurized fluid therein. A sensor is operable to detect afluid pressure in the inlet fluid passage. An outlet fluid passagecommunicates with the inlet fluid passage. A valve seat is disposed at ajuncture of the inlet fluid passage and the outlet fluid passage. Avalve member is mounted for selective movement relative to the valveseat between a closed position for closing fluid communication betweenthe inlet fluid passage and the outlet fluid passage and an openposition for opening fluid communication between the inlet fluid passageand the outlet fluid passage to regulate a fluid pressure in the inletfluid passage. A pre-stressed bender actuator operatively engages thevalve member and is operable to selectively move the valve member to atleast one of the open and closed positions in response to a detectedfluid pressure in the inlet fluid passage by the sensor.

[0018] In accordance with still yet another embodiment of the presentinvention, a valve system includes a fluid chamber and a fluid passagecommunicating with the fluid chamber. A fluid aperture is disposed atthe juncture of the fluid chamber and the fluid passage. A pre-stressedbender actuator is operable to act directly on the fluid aperturebetween a closed position for closing fluid communication between thefluid chamber and the fluid passage and an open position for openingfluid communication between the fluid chamber and the fluid passage.

BRIEF DESCRIPTION OF THE DRAWINGS

[0019]FIG. 1 is a schematic cross-sectional view illustrating a commonrail fuel injector in accordance with one embodiment of the presentinvention;

[0020]FIG. 2 is a view similar to FIG. 1 illustrating a common rail fuelinjector in accordance with a second embodiment of the presentinvention;

[0021]FIG. 3 is a view similar to FIG. 1 illustrating a common rail fuelinjector in accordance with a third embodiment of the present invention;

[0022]FIG. 4 is a view similar to FIG. 1 illustrating a common rail fuelinjector in accordance with a fourth embodiment of the presentinvention;

[0023]FIG. 5 is a view similar to FIG. 1 illustrating a common rail fuelinjector in accordance with a fifth embodiment of the present invention;

[0024]FIG. 6 is a schematic block diagram of an electrohydraulicactuator system in accordance with one embodiment of the presentinvention;

[0025]FIGS. 7A and 7B are schematic cross-sectional views illustratingthe operation of one embodiment of an electrohydraulic actuator inaccordance with the principles of the present invention;

[0026]FIG. 8 is a schematic illustration of one embodiment of mounting apre-stressed electroactive bender actuator used in the electrohydraulicactuator of FIG. 6;

[0027]FIG. 9 is a schematic illustration of a first embodiment of apre-stressed electroactive bender actuator used in the electrohydraulicactuator of FIG. 6;

[0028]FIG. 10 is a schematic illustration of a second embodiment of apre-stressed electroactive bender actuator used in the electrohydraulicactuator of FIG. 6;

[0029]FIG. 11 is a schematic illustration of a third embodiment of apre-stressed electroactive bender actuator used in the electrohydraulicactuator of FIG. 6;

[0030]FIG. 12 is a diagrammatic view of an electronically-controlledfuel injector system in accordance with the principles of the presentinvention;

[0031]FIGS. 13A and 13B are cross-sectional views of the fuel injectorused in the system of FIG. 12 illustrating the states of componentswithin the fuel injector during a preinjection phase of a fuel injectioncycle;

[0032]FIGS. 14A ad 14B are cross-sectional views of the fuel injectorused in the system of FIG. 12 illustrating the states of componentswithin the fuel injector during a pilot injection phase of a fuelinjection cycle;

[0033]FIGS. 15A and 15B are cross-sectional views of the fuel injectorused in the system of FIG. 12 illustrating the states of componentswithin the fuel injector during an injection delay phase of a fuelinjection cycle;

[0034]FIG. 16 is cross-sectional views of the fuel injector used in thesystem of FIG. 12 illustrating the states of components within the fuelinjector during a main injection phase of a fuel injection cycle;

[0035]FIG. 17 is a schematic cross-sectional view illustrating agasoline port injector in accordance with one embodiment of the presentinvention;

[0036]FIG. 18 is a schematic cross-sectional view illustrating agasoline port injector in accordance with a second embodiment of thepresent invention;

[0037]FIG. 19 is a schematic illustration of one embodiment of apre-stressed electroactive bender actuator used in the gasoline portinjector of FIG. 18;

[0038]FIG. 20 is a schematic view illustrating a fluid metering valve inaccordance with one embodiment of the present invention;

[0039]FIG. 21 is a schematic view illustrating a fluid metering valve inaccordance with a second embodiment of the present invention;

[0040]FIG. 22 is a schematic view illustrating a fluid metering valve inaccordance with a third embodiment of the present invention;

[0041]FIG. 23 is a schematic view illustrating a fluid metering valve inaccordance with a fourth embodiment of the present invention;

[0042]FIG. 24 is a schematic view illustrating a relief valve or areducing valve in accordance with one embodiment of the presentinvention;

[0043]FIG. 25 is a schematic view illustrating a direct valve inaccordance with one embodiment of the present invention;

[0044]FIG. 26 is a schematic view illustrating a direct-injectiongasoline injector in accordance with one embodiment of the presentinvention; and

[0045]FIG. 27 is a schematic view illustrating a direct-injectiongasoline injector in accordance with a second embodiment of the presentinvention.

DETAILED DESCRIPTION

[0046] With reference to the Figures, and to FIG. 1 in particular, acommon rail fuel injector 100 a is shown in accordance with theprinciples of the present invention. Fuel injector 100 a includes avalve body 102 having a high-pressure fluid rail 104 extending throughthe body 102 that communicates with a fluid chamber 106 formed in theinjector tip 108. An elongated needle valve 110 is mounted to extendaxially through the valve body 102 and includes a valve tip 112 thatnormally seats in a valve seat 114 to close fluid orifices 116 formed atthe remote end of the injector tip 108. The needle valve 110 is biasedto the closed position by a biasing element, such as by a return spring118, that acts on an annular flange 120 extending radially outwardlyfrom the needle valve 110. The needle valve 110 is mounted forreciprocal movement within the valve body 102 for selectively openingand closing the orifices 116 so that fuel may be injected into an enginecombustion chamber or cylinder of a combustion engine (not shown).

[0047] In accordance with one embodiment of the present invention, asshown in FIG. 1, the needle valve 110 is connected to at least onepiezoelectric device 122, such as a pre-stressed electroactive benderactuator, which may be thermally, mechanically or otherwisepre-stressed, that changes its shape by deforming in opposite axialdirections in response to a control signal applied by an electroniccontrol module ECM (not shown). The control signal may be a voltagesignal applied by the ECM to the bender actuator 122 through a pair ofelectrical leads (not shown). Alternatively, the bender actuator 122 maybe controlled by a current control signal as is known in the art.

[0048] The bender actuator 122 preferably has a cylindrical or diskconfiguration and includes at least one electroactive layer (not shown)positioned between a pair of electrodes (not shown), although otherconfigurations are possible as well without departing from the spiritand scope of the present invention. In a de-energized or static state,the bender actuator 122 is preferably pre-stressed to have a domedconfiguration as shown in FIG. 1. When the electrodes (not shown) of thebender actuator 122 are energized to place the bender actuator 122 in anactuated state, such as when a voltage or current control signal isapplied by the ECM (not shown), the bender actuator 122 displacesaxially by flattening out from the domed configuration. In particular,the bender actuator 122 displaces axially, i.e., flattens out, in onedirection when it is actuated in response to a control signal of onepolarity. In a de-energized state, or in response to a control signal ofan opposite polarity, the bender actuator 122 displaces axially, i.e.,returns to its domed configuration, in an opposite direction. Theapplied control signal may even cause the bender actuator 122 to dome toa greater extent beyond its static domed configuration. The benderactuator 122 is therefore bi-directional in its operation. The benderactuator 122 may be a model TH-5C actuator commercially available fromFace International, Inc. of Norfolk, Va. Other appropriate benderactuators may also be used.

[0049] Bender actuator 122 may comprise a plurality of benders actuators(configured in parallel or in series) that are individually stacked orbonded together into a single multi-layered element. While not shown,those of ordinary skill in the art will appreciate that multiple benderactuators 122 may be mounted in parallel within the valve body 102 toincrease the force applied by the bender actuators 122 to the needlevalve 110 in response to a control signal applied by the ECM (notshown). Alternatively, the bender actuators 122 may be mounted in seriesto increase the stroke of the needle valve 110 upon axial displacementof the bender actuators 122 in response to the control signal.

[0050] The bender actuator 122 is mounted within the valve body 102 by aclamping and load ring assembly, illustrated diagrammatically at 124.The structure and operation of the clamping and load ring assembly 124will be described in detail below in connection with FIGS. 7A, 7B, 8 and11. Briefly, the assembly 124 includes upper and lower clamping rings(not shown) that support the bender actuator 122 at its peripheral edgebetween the pair of clamping rings. A load ring 126 of the assembly 124is used to preload or prestress the bender actuator 122 to apredetermined spring constant and/or axial displacement by adjusting theclamping force applied to the bender actuator 122 by the pair ofclamping rings (not shown). Increasing the clamping force on the benderactuator 122 reduces an axial displacement of the bender actuator 122 toa control signal of predetermined magnitude. Conversely, decreasing theclamping force results in a greater axial displacement of the benderactuator 122 to the control signal of predetermined magnitude.

[0051] As shown in FIG. 1, the needle valve 110 is connected to thebender actuator 122 so that the needle valve 110 will travel axiallywithin the valve body 102 upon axial displacement of the bender actuator122 from the domed, or unactuated configuration shown in FIG. 1 to aflattened, or actuated position (not shown). In one embodiment of thepresent invention, the needle valve 110, or at least a portion thereofadjacent to the bender actuator 122, is preferably made from anelectrically nonconducting material, such as zirconia for example. Aswill be appreciated, the needle valve 110 may be fabricated of otherelectrically insulating materials known to those skilled in the art.Alternatively, the end of the needle valve 110 adjacent the benderactuator 122 may be constructed to have an electrically nonconductiveend.

[0052] In accordance with one embodiment, connection of the needle valve110 with the bender actuator 122 is achieved by forming a hole (notshown) near the center of the bender actuator 122. An electricallynonconductive sleeve (not shown) having an electrically nonconductiveannular flange 128 is inserted through the hole (not shown) so that theflange 128 contacts a major surface 130 of the bender actuator 122. Anelectrically nonconductive washer 132 is mounted in contact with anopposite major surface 134 of the bender actuator 122. An electricallyconductive fastener 136, such as a screw, is inserted through thenonconductive sleeve (not shown) and threadably engaged with one end ofthe needle valve 110. Alternatively, an electrically nonconductivefastener 136 may be inserted directly through the hole (not shown) inthe bender actuator 122 to threadably connect with one end of the needlevalve 110. As will be appreciated, instead of using a fastener 136, theend of the needle valve 110 may be rigidly connected to the benderactuator 122 by adhesives, bonding or attaching by other means. With thebender actuator 122 rigidly connected to the needle valve 110, thebender actuator 122 is capable of moving the needle valve 110bidirectionally with the bidirectional operation of the bender actuator122. While not shown, it will be appreciated that needle valve 110 maynot be rigidly connected to the bender actuator 122. Rather, one end ofthe needle valve 110 remote from the valve tip 112 engages major surface134 of the bender actuator 122 so that the needle valve 110 will travelaxially within the valve body 102 upon axial displacement of the benderactuator 122 from the domed or unactuated configuration shown in FIG. 1to a flattened, or actuated position (not shown).

[0053] In operation of the common rail fuel injector 100 a, the returnspring 118 biases the needle valve 110 to a closed position so that thevalve tip 112 seats in the valve seat 114 to close the orifices 116.Fuel is delivered to the fluid chamber 106 under pressure through thehigh pressure rail 104. During an injection cycle, the ECM (not shown)applies a control signal to the bender actuator 122 that causes thebender actuator 122 to deform or displace axially by flattening out. Asthe bender actuator 122 flattens out in response to the control signal,the needle valve 110, by virtue of its rigid connection to the benderactuator 122, lifts off of the valve seat 114 against the force ofreturn spring 118 to open the orifices 116 for an injection of fuel.After the injection cycle is complete, the control signal is eitherdiscontinued, or the polarity of the control signal is reversed, tocause the bender actuator 122 to return to its domed configuration asshown in FIG. 1. The return spring 118 assists in returning the needlevalve 110 to its closed position in contact with valve seat 114 to sealthe orifices 116.

[0054] Referring now to FIG. 2, a common rail fuel injector 100 b isshown in accordance with an alternative second embodiment of the presentinvention, where like numerals represent like parts to the common railfuel injector 100 a of FIG. 1. In this embodiment, the return spring 118is eliminated so that the bi-directional operation of the benderactuator 122 is used to move the needle valve 110 to both its open andclosed positions. The spring rate of the bender actuator 122 may beadjusted by the clamping and load ring assembly 124 to pre-load theneedle valve 110 against the valve seat 114. Alternatively, the springrate of the bender actuator 122 may be controlled by the material and/orthickness selection of the bender actuator 122. During an injectioncycle, the bender actuator 122 is energized to move the needle valve 110to its open position as described in detail above. After the injectioncycle is complete, the polarity of the control signal is preferablyreversed to cause the bender actuator 122 to return to its domedconfiguration as shown in FIG. 2 and thereby return the needle valve 110to its closed position in contact with valve seat 114 to seal theorifices 116.

[0055] Referring now to FIG. 3, a common rail fuel injector 100 c isshown in accordance with an alternative third embodiment of the presentinvention, where like numerals represent like parts to the common railfuel injector 100 a of FIG. 1. In this embodiment, the fuel injector 100c includes the high-pressure fluid rail 104 extending through the valvebody 102 that communicates with the fluid chamber 106 formed in theinjector tip 108. An outwardly opening, elongated check valve 138 ismounted to extend axially through the valve body 102 and includes aclosing head 140 that normally seats in a conically-shaped valve seat142 to close a fluid orifice 144 formed at the remote end of theinjector tip 108. The check valve 138 is biased to the closed positionby a biasing element, such as by a return spring 146, that acts on anannular flange 148 extending radially outwardly from the check valve138. The check valve 138 is mounted for reciprocal movement within thevalve body 102 for selectively opening and closing the orifice 144 sothat fuel may be injected into an engine combustion chamber or cylinderof a combustion engine (not shown).

[0056] In this embodiment, one end of the check valve 138 remote fromthe closing head 140 engages at least one bender actuator 122. The checkvalve 138 engages the bender actuator 122 so that the check valve 138will travel axially within the valve body 102 upon axial displacement ofthe bender actuator 122 from the domed, or unactuated configurationshown in FIG. 3 to a flattened, or actuated position (not shown).

[0057] In operation of the common rail fuel injector 100 c, the returnspring 146 biases the outwardly opening check valve 138 to a closedposition so that the closing head 140 seats in the conically-shapedvalve seat 142 to close the orifice 144. Fuel is delivered to the fluidchamber 106 under pressure through the high pressure rail 104. During aninjection cycle, the ECM (not shown) applies a control signal to thebender actuator 122 that causes the bender actuator 122 to deform ordisplace axially by flattening out. As the bender actuator 122 flattensout in response to the control signal, the check valve 138, by virtue ofits engagement with the bender actuator 122, is pushed off of theconically-shaped valve seat 142 against the force of return spring 146to open the orifice 144 for an injection of fuel. After the injectioncycle is complete, the control signal is either discontinued, or thepolarity of the control signal is reversed, to cause the bender actuator122 to return to its domed configuration as shown in FIG. 3. The returnspring 146 assists in returning the check valve 138 to its closedposition so that the closing head 140 engages the conically-shaped valveseat 142 to seal the orifice 144.

[0058] Referring now to FIG. 4, a common rail fuel injector 100 d isshown in accordance with an alternative fourth embodiment of the presentinvention, where like numerals represent like parts to the common railfuel injector 100 c of FIG. 3. In this embodiment, the elongated checkvalve 138 is rigidly connected to the bender actuator 122 as describedin detail above in connection with FIG. 1 so that the bi-directionaloperation of the bender actuator 122 is used to move the check valve 138to both its open and closed positions. The rigid connection of the checkvalve 138 to the bender actuator 122 permits the return spring 146 to beeliminated so that the bender actuator 122 provides the necessary forceto return the check valve 138 to its closed position. As described indetail above, the spring rate of the bender actuator is adjusted by theclamping and load ring assembly 124 to pre-load the check valve 138against the conically-shaped valve seat 142.

[0059] Referring now to FIG. 5, a common rail fuel injector 100 e isshown in accordance with an alternative fifth embodiment of the presentinvention, where like numerals represent like parts to the common railfuel injector 100 a of FIG. 1. Fuel injector 100 e includes a valve body150 having a high-pressure fluid rail 152 extending through the body 150that communicates with a fluid chamber 154 formed in the injector tip108 and a control fluid chamber 156 formed in the valve body 150. Aneedle valve 158 is mounted to extend axially through the valve body 150and includes a valve tip 160 that normally seats in a valve seat 162 toclose fluid orifices 164 formed at the remote end of the injector tip108. The needle valve 158 is biased to the closed position by a biasingelement, such as by a return spring 166, that acts on a head 168 of theneedle valve 158. The needle valve 158 is mounted for reciprocalmovement within the valve body 150 for selectively opening and closingthe orifices 164 so that fuel may be injected into an engine combustionchamber or cylinder of a combustion engine (not shown).

[0060] The high-pressure fluid delivered to the control chamber 156above the valve 158 and to the fluid chamber 154 in the injector tip 108creates a force balance along with the return spring 166. The highpressure fluid is retained in the control chamber 156 by a control valve170 that seals the control chamber 156 from a drain 171. The controlvalve 170 is biased to a closed position against valve seat 172 by abiasing element, such as by a return spring 174, that acts on a closinghead 176 of the control valve 170. The control valve 170 is mounted forreciprocal movement within the valve body 150 for selectively openingand closing a fluid passage from the control chamber 156 to the drain171.

[0061] Further referring to FIG. 5, one end of the control valve 170remote from the closing head 176 engages at least one bender actuator122. The control valve 170 engages the bender actuator 122 so that thecontrol valve 170 will travel axially within the valve body 150 uponaxial displacement of the bender actuator 122 from the domed, orunactuated configuration shown in FIG. 5 to a flattened, or actuatedposition (not shown).

[0062] In operation of the common rail fuel injector 100 e, the returnspring 174 biases the control valve 170 to a closed position so that theclosing head 176 seats against the valve seat 172 to close the fluidpassage from the control chamber 156 to the drain 171. Fuel is deliveredunder pressure from the high pressure rail 152 to the fluid chamber 154and to the control chamber 156 to create a force balance along with thereturn spring 156.

[0063] To initiate an injection of fuel from the orifices 164, the ECM(not shown) applies a control signal to the bender actuator 122 thatcauses the bender actuator 122 to deform or displace axially byflattening out. As the bender actuator 122 flattens out in response tothe control signal, the control valve 170, by virtue of its engagementwith the bender actuator 122, is pushed off of the valve seat 172against the force of return spring 174 to open the control chamber 156to drain 171. This results in a pressure differential being created thatlifts the needle valve 158 off of the valve seat 162 against the forceof return spring 156 and thereby open the orifices 164 for an injectionof fuel.

[0064] After the injection cycle is complete, the control signal iseither discontinued, or the polarity of the control signal is reversed,to cause the bender actuator 122 to return to its domed configuration asshown in FIG. 5. The return spring 174 assists in returning the controlvalve 170 to its closed position so that the closing head 176 engagesthe valve seat 172 to seal the fluid passage from the control chamber156 to the drain 171. High pressure is restored to the control chamber156 to create a force balance along with the return spring 156 asdescribed in detail above. This results in the needle valve 158 movingto the closed position against valve seat 162 to close the orifices 164.While not shown, those of ordinary skill in the art will appreciate thatmultiple bender actuators 122 may be mounted in parallel within thevalve body 150 to increase the force applied by the bender actuators 122to the control valve 170 in response to a control signal applied by theECM (not shown). Additionally, while not shown, it will be appreciatedthat the control valve 170 could be rigidly connected to the benderactuator 122 so that the return spring 174 is eliminated. In thisembodiment, the bi-directional operation of the bender actuator 122 isused to move the control valve 170 to both its open and closed positionsand thereby control operation of the needle valve 158 as described indetail above.

[0065] With reference to FIG. 6, an electrohydraulic actuator 310comprises a hydraulic valve 314 and an electromechanical actuator 312,such as a prestressed electroactive bender actuator, which may bethermally, mechanically or otherwise pre-stressed, for example. Theelectrohydraulic actuator 310 receives pressurized hydraulic fluid froma fluid source 335, and the electrohydraulic actuator 310 is fluidlycoupled to, and controls the operation of, a device 315 such as ahydraulic valve 314 for example.

[0066] In general, to operate the device 315, an electronic control unit328, such as an electronic control module (ECM) for example, provides acommand signal to the bender actuator 312 causing the bender actuator312 to switch from a first to a second operating state. The hydraulicvalve 314 switches from a first to a second operating state as afunction of a change in state of the bender actuator 312. The device 315switches from a first to a second operating state as a function of achange in state of the hydraulic valve 314. The bidirectional capabilityof the bender actuator 312 is used to switch or return the hydraulicvalve 314 and the device 315 from their respective second states totheir respective first states.

[0067] Referring to FIG. 7A, in accordance with the principles of thepresent invention, the bender actuator 312 comprises a prestressedelectroactive bender actuator, which may be thermally, mechanically orotherwise pre-stressed, that changes its shape by deforming in oppositeaxial directions in response to a control signal applied by the ECM 328.The control signal may be a voltage signal applied from the ECM 328 tothe bender actuator 312 though electrical conductors. The benderactuator 312 normally has a circular or disk configuration and includesat least one electroactive layer (not shown) positioned between a pairof electrodes (not shown), although other configurations are possible aswell without departing from the spirit and scope of the presentinvention. In an unactuated or static state, the bender actuator 312 ispreferably prestressed to have a domed configuration as shown in FIG.7A. When the electrodes are energized to place the bender actuator 312in an actuated state, the bender actuator 312 displaces axially to aless domed configuration as shown in FIG. 7B. The bender actuator 312may be a model TH-5C commercially available from Face International,Inc. of Norfolk, Va. Other appropriate actuators may also be used. Oneor more bender actuators 312 may comprise a plurality of benderactuators (configured in parallel or in series) that are individuallystacked or bonded together into a single multi-layered element.

[0068] The bender actuator 312 is disposed within a cavity 318 withinthe housing 316 and is supported at its peripheral edge 320 betweenlower and upper clamp rings 322, 324 respectively. The clamp rings arenormally made from a stiff electrically nonconductive material. Thelower clamp ring 322 is generally L-shaped in cross section and has agenerally cylindrical inner side surface 321 that locates the peripheraledge 320 of the bender actuator 312. The lower clamp ring 322 has anannular support surface 323 that supports one side of the benderactuator 312 around its peripheral edge 320. The upper clamp ring 324 isalso generally L-shaped in cross section and has a bearing surface 325that contacts an opposite side of the bender actuator 312 around itsperipheral edge 320.

[0069] A load ring 326 threadably engaged within the housing is used toprestress the bender actuator 312 with a clamping force. As the loadring 326 is tighten and loosened, the clamping force is respectivelyincreased and decreased on the peripheral edge 320 of the benderactuator 312 via the upper clamp ring 324. Increasing the clamping forceon the bender actuator 312 reduces an axial displacement of the benderactuator 312 in response to a given control signal magnitude.Conversely, decreasing the clamping force results in a greater axialdisplacement. In the embodiment of FIG. 7A, the load ring 326 applies aclamping force around the whole peripheral edge 320 of the benderactuator 312. As will be appreciated, in an alternative embodiment, thebearing surface of the upper clamp ring 324 may be notched or cut out atdifferent locations around its circumference. Thus, no clamping force isdirectly applied to the portions of the peripheral edge 320 of thebender actuator 312 that are directly opposite the cutouts in thebearing surface of the upper clamp ring 324. Alternatively, a staticload may be applied to the bender actuator 312 when the electrohydraulicactuator 310 is bolted together so that the load ring 326 is notthreadably engaged to the housing 316 according to this embodiment.

[0070] The hydraulic valve 314 is comprised of a movable valve element330, such as, a poppet for example, disposed in a cavity 332 of a valvebody 334 on which the housing 316 is mounted. The hydraulic valve 314 ofFIG. 2A is a three-way two-position valve. As will be appreciated, othercomparably functioning valves may be used in place of the poppet 330.Hydraulic fluid is provided from a source of pressurized fluid 335 via asupply passage 336 that intersects the cavity 332. Hydraulic fluid isreturned to the fluid source 335 via drain passages 338 that alsointersects the cavity 332. Operation of the hydraulic valve 314 connectseither the supply passage 336 or the drain passage 338 to a controlpassage 340. As will be appreciated, the two-dimensional depiction ofthe passages 336, 338, 340 in FIG. 2A is schematic in nature. Often thehydraulic valve 314 is manufactured such that the passages 336, 338 and340 intersect the cavity 332 at different circumferential locations ofthe cavity 332.

[0071] In FIG. 7A, the bender actuator 312 is illustrated in its domed,unactuated, quiescent position, that is, its prestressed mechanicalstate; and the poppet 330 is shown in its first position. The benderactuator 312 operates in response to the ECM 328 supplying commandsignals in the form of biasing voltages of different polarities andmagnitudes. The unactuated state of the bender actuator 312 is achievedin response to the ECM 328 providing a first command signal to thebender actuator 312, such as, a DC biasing voltage of a first polarity.When in that state, a center portion 342 of the bender actuator 312 isdisplaced vertically upward to a flexed or domed position. An actuatingpin or portion 344 of the poppet 330 is mechanically biased against alower side of the center portion 342 of the bender actuator 312 by abiasing element, such as, a return spring 346 for example.

[0072] The actuating pin 344 is normally made from an electricallynonconducting material, such as, zirconia for example. As will beappreciated, the actuating pin may be fabricated of other electricallyinsulating materials known to those skilled in the art. Alternatively,the end of the actuating pin 344 that is in contact with the benderactuator 312 may be constructed to have an electrically nonconductivetip.

[0073] In the first position, the poppet 330 has a first annular sealingarea 348 that is separated from an annular lower seat 350 on the valvebody 334. Therefore, pressurized hydraulic fluid is released to flowfrom the supply passage 336 to the control passage 340. When in thefirst position, the poppet 330 has a second annular sealing area 352that is engaged with an annular upper seat 354, thereby blocking theflow of hydraulic fluid from the control passage 340 to the drainpassage 338.

[0074] When it is desired to operate or change the state of thehydraulic valve 314, the ECM 328 provides a second command signal to thebender actuator 312, such as, a first DC biasing voltage of a differentpolarity from the first command signal. The second command signal causesthe bender actuator 312 to flex in a generally vertically downwarddirection to a less domed or slightly domed position. The downwardmotion of the bender actuator 312 overcomes the biasing force of thereturn spring 346 as the bender actuator 312 moves to its actuated,second position as illustrated in FIG. 7B. It should be noted that ifthe first command signal is removed, the bender actuator 312 willtemporarily remain in the position illustrated in FIG. 7B until itscharge sufficiently leaks off. Therefore, substantially less power isrequired to maintain the bender actuator 312 than other actuators, suchas, a solenoid for example.

[0075] Motion of the bender actuator 312 downward pushes the actuatorportion 342 and the poppet 330 downward to its second position. With thepoppet 330 at its second position, the second annular sealing area 352is separated from the annular upper seat 354, thereby opening thecontrol passage 340 to the drain passage 338. Further, the first annularsealing area 348 engages the annular lower seat 350 on the valve body334, and pressurized hydraulic fluid from the supply passage 336 isblocked from the control passage 340.

[0076] The hydraulic valve 314 remains in the state illustrated in FIG.7B until the ECM 328 provides a different or the first command signal.When the ECM 328 again applies the first command signal to the benderactuator 312, the bender actuator 312 moves generally upward until itachieves the unactuated, domed first position illustrated in FIG. 7A. Itshould be noted that if the first command signal is removed, the benderactuator 312 will temporarily remain in the position illustrated in FIG.7A until its charge sufficiently leaks off. As the bender actuator 312moves upward, the return spring 346 biases the poppet 330 upward againstthe center portion 342 of the bender actuator 312. As the poppet movesupward, the second annular sealing area 352 engages against the annularupper seat 354, thereby again closing the control passage 340 from thedrain passage 338. Further, the first annular sealing area 348 separatesfrom the annular lower seat 350 on the valve body 334, therebyinitiating flow of pressurized hydraulic fluid to the control passage340.

[0077] The operation of the return spring 346 moves the poppet 330 witha relatively high force, and the poppet 330 impacts the upper valve seat354 at a relatively high velocity. Such repeated high velocity impact ofthe poppet 330 against the seat 348 causes wear and reduces the usefullives of the poppet 330 and seat 348. The bender actuator 312 is aproportional and bidirectional actuator, and those features can be usedto cushion or reduce the impact of the poppet 330 on the seat 354. Afterthe first command signal is provided to the bender actuator 312 to moveit back toward its first position as illustrated in FIG. 7A, the poppet330 is moved towards its seat by the return spring 346.

[0078] As the poppet 330 moves toward the upper seat 354, the ECM 328applies to the bender actuator 312 a third command signal or biassimilar to, but less than, the first command signal. The third commandsignal causes the bender actuator 312 to move through a small upwarddisplacement to a slightly domed third position. That third positionincreases the resistance force against the operation of the returnspring 346. With the resistance force, the velocity of the poppet 330 isreduced as is the impact force of the poppet 330 on the seat 354. Aswill be appreciated, the ECM 328 can provide command signals to benderactuator 312 that control both the displacement or position, velocityand acceleration of the bender actuator 312 in order to more preciselycontrol the operation of the poppet 330.

[0079] In the described embodiment with respect to FIG. 6, the clamprings 322, 324 are illustrated as generally L-shaped members in crosssection in which the lower clamp ring 322 has a side surface 321 forlocating the peripheral edge 320 of the bender actuator 312. As will beappreciated, other configurations of clamp rings may be used. Forexample, referring to FIG. 8, upper and lower clamp rings 360, 362 aredisposed within the cavity 318 of the housing 316. The lower clamp ring362 has an annular support surface 364 for supporting a lower side ofthe bender actuator 312 about the peripheral edge 320. The upper clampring 360 has an annular bearing surface 366 for applying a clampingforce around the peripheral edge 320 on an opposite side of the benderactuator 312. The outer circumferential surfaces 368, 370 of the upperand lower rings 360, 362 locate the rings inside the cavity 318. Theload ring 326 functions as previously described with respect to FIG. 6to apply a clamping force to the peripheral edge 320 of the benderactuator 312. As previously discussed, the bearing surface 366 of theupper clamp ring 360 may be cut out at different locations to vary theapplication of the clamping force against the bender actuator 312.

[0080] The clamp rings 322, 324, 360, 362 are normally made of a stiff,electrically nonconductive material. As will be appreciated, the ringsmay be made of a conductive material if the surfaces of the benderactuator 312 contacting the rings is protected with a dielectriccoating. Alternatively, one of the above embodiments may be used witheach ring. As a further alternative, a compliant material such as rubberor a “VITON” material may be used between the clamp rings and the benderactuator in order to improve the actuator loading.

[0081] In the described embodiment, the bender actuator 312 is circularin nature. Referring to FIG. 9, the bender actuator 312 a may bequadrilateral, for example, square or rectangular. Upper and lowerclamping members 372, 374, respectively, extend along sides 376 of thebender actuator 312 a that are parallel to its axis of curvature. Theclamping members 372, 374 secure the sides 376 of the bender actuator312 a in a similar manner as described with respect to FIGS. 1 and 2.Further, the clamping members 372, 374 may be of differentconfigurations similar to the clamp rings 322, 324 described earlier. Aswill be appreciated, the bender actuator 312 a may be of any shape orsize that permits it to execute the functions described herein.

[0082] Referring to FIG. 10, a bender actuator 312 b may be supportedalong only a single side 378 between upper and lower clamping members380, 382, respectively. In this embodiment, the distal end 384 of thebender actuator 312 b experiences a linear displacement in response tobiasing voltages of opposite polarities.

[0083] In the described embodiment, the electromechanical benderactuator 312 is applied to a hydraulic valve 314 that is described as a2-position 3-way poppet valve. The concept of the present invention canbe extended to an N-position M-way poppet valve. Further, the presentinvention can be used with a spool valve or any other linearlytranslatable valve.

[0084] In the described embodiment, the poppet 330 is held in contactwith the bender actuator 312 by a return spring 346. While returnsprings are widely used in combination with valves, in this application,a return spring represents a significant force to be opposed by thebender actuator 312. Further, the variability of the spring constant ofthe return spring 346 can have a significant effect on the performanceof fast proportional valves. As an alternative to the use of a returnspring, referring to FIG. 11, a hole 386 is formed at the center of thebender actuator 312 c. A fastener 388, such as, a screw for example, isthreadably engaged with the end of the actuating pin 344. Thus, with thebender actuator 312 c rigidly connected to the actuating pin 344, thebender actuator 312 c is now capable of moving the actuating pin 344 andpoppet 330 bidirectionally with the bidirectional operation of thebender actuator 312 c. Therefore, the need for a return spring iseliminated. As will be appreciated, instead of using a fastener 388, theend of the actuating pin 344 may be rigidly connected to the benderactuator 312 c by adhesives, bonding or attaching by other means.

[0085] With reference to the Figures, and to FIG. 12 in particular, anexemplary embodiment of an electronically-controlled fuel system 410 foremploying the present invention is shown. The exemplary fuel injectionsystem 410 is adapted for a direct-injection diesel-cycle reciprocatinginternal combustion engine. However, it should be understood that thepresent invention is also applicable to other types of engines, such asrotary engines, or modified-cycle engines, and that the engine maycontain one or more engine combustion chambers or cylinders. The fuelsystem 410 includes a fuel injector 412, apparatus 413 for supplyingfuel to each injector 412, and apparatus 414 for electronicallycontrolling each injector 412.

[0086] The engine has at least one cylinder (not shown) wherein eachcylinder intersects one or more separate injector bores (not shown),each of which receives a fuel injector 412 in accordance with theprinciples of the present invention. The fuel injector 412 shouldpressurize a supply of fuel from the fuel supply 413, atomize thepressurized fuel by pumping it through one or more output orifices 510,deliver the correct amount of pressurized fluid to the combustionchamber portion of the cylinder and evenly disperse the fuel throughoutthe combustion chamber. Each injector is comprised of anelectrohydraulic injector drive 415 and an injector actuator 423. Theinjector drive 415 is comprised of an actuator drive 418 and anelectromechanical actuator 419, such as a prestressed electroactivebender actuator, which may be thermally, mechanically or otherwiseprestressed, for example. The actuator drive 418 is fluidly coupled to asource of or drain for pressurized fluid 422, such as a hydraulic oilfor example, and comprises a main valve 421 and a hydraulic pilot valve420 responsive to the operation of the bender actuator 419. The injectoractuator 423 is comprised of a pressure intensifier 416 and an injectionvalve system 417.

[0087] In general, to operate the injection valve system 417, theelectronic control 414 provides a command signal to the bender actuator419 causing the bender actuator 419 to move through a displacement andswitch from a first to a second operating state. The actuator drive 418switches from a first to a second operating state as a function of achange in state of the bender actuator 419. More specifically, as thebender actuator 419 moves through its displacement, it also moves thepilot valve 420. Movement of the pilot valve 420 redirects pressurizedhydraulic fluid and changes the state of the main valve 421. Further,the redirected hydraulic fluid cause the pressure intensifier 416 andthe injection valve system 417 to switch from first to second operatingstates as a function of the change in state of the actuator drive 418,thereby either initiating a supply of, or terminating a supply of,pressurized fuel from the output orifice 510 of the fuel injector 412.

[0088] The fuel supplying apparatus 413 typically includes a fuel tank424, a fuel supply passage 425 fluidly coupled between the fuel tank 424and an inlet port 429 of the fuel injector 412, a relatively lowpressure fuel transfer pump 426, one or more fuel filters 427, and afuel drain passage 428 fluidly coupled between the injector 412 and thefuel tank 424. If desired, fuel passages may be disposed in the head ofthe engine that are fluidly coupled with the fuel injector 412 and oneor both of the passages 425, 428.

[0089] The electronic control apparatus 414 preferably includes anelectronic control module (ECM) 430 which controls at least: (1) fuelinjection timing and pressure; (2) total fuel injection quantity duringan injection cycle; (3) the phases during each segment of each injectioncycle; (4) the number of separate injection segments during eachinjection cycle; (5) the time interval(s) between the injectionsegments; and (6) the fuel quantity delivered during each injectionsegment of each injection cycle.

[0090] Normally, each injector 412 is a unit injector wherein theinjector drive 415, pressure intensifier 416 and injection valve system417 are disposed in a common housing 432. Although shown as a unitizedinjector 412, the injector 412 could alternatively be of a modularconstruction wherein the pressure intensifier 416 is separate from theinjection valve system 417. As a further alternative, the injector drive415 may be separated from the pressure intensifier 416.

[0091] Referring to FIG. 13A, in accordance with the principles of thepresent invention, the bender actuator 419 comprises a prestressedelectroactive bender actuator, which may be thermally, mechanically orotherwise prestressed, that changes its shape by deforming in oppositeaxial directions in response to a control signal applied by the ECM 430.The control signal may be a voltage signal applied from the ECM 430 tothe bender actuator 419 through a pair of electrical conductors 434. Thebender actuator 419 normally has a circular or disk configuration andincludes at least one electroactive layer (not shown) positioned betweena pair of electrodes (not shown), although other configurations arepossible as well without departing from the spirit and scope of thepresent invention. In an unactuated or static state, the bender actuator419 is preferably prestressed to have a domed configuration as shown inFIG. 13A. When the electrodes are energized to place the bender actuator419 in an actuated state, the bender actuator 419 displaces axially to aless domed configuration as shown in FIG. 13B.

[0092] The bender actuator 419 may be a model TH-5C commerciallyavailable from Face International, Inc. of Norfolk, Va. Otherappropriate actuators may also be used. One or more bender actuators 419may comprise a plurality of bender actuators (configured in parallel orin series) that are individually stacked or bonded together into asingle multi-layered element.

[0093] Referring to FIGS. 13A and 13B, the bender actuator 419 isdisposed within the housing 432 and is supported at its peripheral edge436 between lower and upper clamp rings 438, 440, respectively. Theclamp rings are normally made from a stiff electrically nonconductivematerial. The lower clamp ring 438 is generally L-shaped in crosssection and has an annular support surface for supporting a lower sideof the bender actuator 419 around its peripheral edge 436. The upperclamp ring 440 is also generally L-shaped in cross section and has abearing surface that contacts an upper side of the bender actuator 419around its peripheral edge 436. As will be appreciated, otherconfigurations of the clamp rings 438, 440 may be used.

[0094] A load ring 442, threadably engaged within the housing 432, isused to prestress the bender actuator 419 with a clamping force. As theload ring 442 is tighten and loosened, the clamping force isrespectively increased and decreased on the peripheral edge 436 of thebender actuator 419 via the upper clamp ring 440. Increasing theclamping force on the bender actuator 419 reduces an axial displacementof the bender actuator 419 in response to a given control signalmagnitude. Conversely, decreasing the clamping force results in agreater axial displacement. In the embodiment of FIG. 2A, the load ringapplies a clamping force around the whole peripheral edge 436 of thebender actuator 419. As will be appreciated, in an alternativeembodiment, the bearing surface of the upper clamp ring 440 may benotched or cut out at different locations around its circumference.Thus, no clamping force is directly applied to the portions of theperipheral edge 436 of the bender actuator 419 that are directlyopposite the cutouts in the bearing surface of the upper clamp ring 440.It will be appreciated by those of ordinary skill in the art that otherclamping configurations are possible as well, as described in detailabove, without departing from the spirit and scope of the presentinvention.

[0095] The hydraulic pilot valve 420 is comprised of a movable valve444, such as a poppet for example, that is disposed in a cavity 445 inthe housing 432. The pilot valve 420 of FIGS. 2A and 2B is a three-waytwo-position valve. As will be appreciated, other comparable functioningvalves may be used in place of the poppet 444. The injector housing 432has an inlet port 446 fluidly coupled with the supply line 447 of thehydraulic fluid source 422. Pressurized hydraulic fluid from the fluidsource 422 passes through a supply passage 448 that intersects cavity445 of the housing 432. Hydraulic fluid is returned to the fluid source422 via drain passages 450 that also intersect the cavity 445. Operationof the pilot valve 420 connects either the supply passage 448 or thedrain passage 450 to a control passage 452. As will be appreciated, thetwo-dimensional depiction of the passages 448, 450, 452 in FIG. 2A areschematic in nature. Often the pilot valve 420 is manufactured such thatthe passages 448, 450, 452 intersect the cavity 445 at differentcircumferential locations of the cavity 445.

[0096] In FIGS. 13A and 13B, the bender actuator 419 is illustrated inits domed, quiescent, unactuated state or position. When in theunactuated state, a center portion of the bender actuator 419 isdisplaced vertically upward to a flexed or domed position. An actuatingpin or portion 454 of the poppet valve 444 is mechanically biasedagainst a lower side of the center portion of the bender actuator 419 bya biasing element, such as a return spring 456 for example.

[0097] The actuating pin 454 is normally made from an electricallynonconducting material, such as zirconia for example. As will beappreciated, the actuating pin may be fabricated of other electricallyinsulating materials known to those who are skilled in the art.Alternatively, the end of the actuating pin 454 that is in contact withthe bender actuator 419 may be constructed to have an electricallynonconductive tip.

[0098] In the position illustrated in FIGS. 13A and 13B, the poppetvalve 444 has a first annular sealing area 458 that is separated from anannular lower seat 460 on the housing 432. Therefore, pressurizedhydraulic fluid is free to flow from the supply passage 448 to thecontrol passage 452. Further, the poppet 444 has a second annularsealing area 462 that is engaged with an annular upper seat 464, therebyblocking the flow of hydraulic fluid from the control passage 452 to thedrain passage 450.

[0099] With the poppet 444 in the position illustrated in FIGS. 13A and13B, the pressurized hydraulic fluid is provided to a bottom 466 of themain valve 421, such as a spool valve for example. The supply passage448 also intersects an external annular passage or annulus 471 on thespool valve 421. Holes 473 provide a fluid connection between theannulus 471 and a fluid cavity 470. Thus, the supply passage 448provides pressurized fluid to the cavity 470 that is contiguous with anupper end or top 472 of the spool valve 421. The spool valve is designedsuch that when the pressurized hydraulic fluid is applied to ends, theforces applied by the pressurized hydraulic fluid are equal andopposite. With equal fluid forces, the spool valve 421 is biased towarda closed position illustrated in FIG. 13A by a biasing element 474, suchas a return spring for example.

[0100] With the spool valve 421 closed, the fluid passage 476 is fluidlyconnected to an annular fluid path or annulus 475 that in turnintersects a drain line 477. Thus, any fluid pressure in the fluid path476 is relieved when the spool valve 421 is in its upper, closedposition. Further, with the spool valve 421 in its closed position,hydraulic fluid in the supply passage 448 is blocked from entering thetop of the hydraulic fluid passage 476 that is connected to a cavity 498containing an intensifier piston 480. With no hydraulic fluid forcebeing applied to the top of the pressure intensifier 416, a biasingelement 482, such as a return spring for example, holds the intensifierpiston 480 at its uppermost position within the cavity 498.

[0101] With the poppet valve 420 in the position shown in FIGS. 13A and13B, pressurized hydraulic fluid in control passage 452 is directed to acavity 484 above a check piston 486 connected to a nozzle check valve488. Pressurized hydraulic fluid above the check piston 486 forces thecheck piston 486 and nozzle valve 488 downward. An end 506 of the nozzlecheck valve 488 is sealingly engaged against an interior surface of thetip 490 of the fuel injector 412, thereby closing the nozzle check valve488 and prohibiting the flow of fuel from its output orifice 510.

[0102] The fuel injector 412 operates with a split injection cycle thathas the following five phases of injection: preinjection, pilotinjection, injection delay, main injection and fill. The preinjectionphase exists when the engine is running and the injector 412 is betweenfiring cycles. The preinjection phase is illustrated by the states ofthe various components of the fuel injector 412 illustrated in FIGS. 13Aand 13B. Hydraulic fluid pressure on the spool valve 421 is balanced;and therefore, the spool valve 421 is held closed by the return spring474, thereby stopping a flow of pressurized hydraulic fluid to theintensifier piston 480.

[0103] In its raised, closed position, the spool valve 421 separatesfrom, and mechanically releases, spool pin 496 and ball check valve 492.Therefore, the pressure of any hydraulic fluid in fluid passage 476 isreleased around ball check valve 492 and out vent line 494. Thus, thepressure intensifier 416 is maintained inactive; and pressurizedhydraulic fluid in the control passage 452 holds the check piston 486and nozzle check valve 488 closed. Therefore, fuel received at the inletport 429 is not injected into a cylinder.

[0104] At the appropriate time, the ECM 430 initiates the pilotinjection phase by providing a first command signal to the benderactuator 419, such as a DC biasing voltage of a first polarity.Referring to FIGS. 14A and 14B, the first command signal causes thebender actuator 419 to flex in a first direction, such as a generallyvertically downward direction as viewed in FIG. 13A to a less domed orslightly domed, actuated, first position. It should be noted that withactuators currently available, such actuators never reach a flat state;and they will be destroyed by any flexure past center or a flat state.

[0105] The downward movement of the bender actuator 419 overcomes thebiasing force of the return spring 456 as the bender actuator 419 movesto its actuated, first position. It should be noted that if the firstcommand signal is removed, the bender actuator 419 will temporarilyremain in the position illustrated in FIGS. 14A and 14B until its chargesufficiently leaks off. Therefore, substantially less power is appliedto maintain the bender actuator 419 and other actuators, such as asolenoid for example.

[0106] Movement of the bender actuator 419 downward pushes the actuatorpin 452 and poppet 420 downward to a first position. With the poppetvalve 420 at its first position, the first annular sealing area 458engages the annular lower seat 460, and the pressurized hydraulic fluidfrom the supply passage 448 is blocked from the control passage 452.Further, the second annular sealing area 462 is separated from theannular upper seat 464, thereby opening the control passage 452 to thedrain passage 450. Thus, hydraulic pressure is removed from the bottomside 466 of the spool valve 421.

[0107] The pressure head in the cavity 470 at the top 472 of the spoolvalve 421 overcomes the force exerted by the return spring 474, and thespool valve 421 moves vertically downward to an open position. As thespool valve 421 moves downward, it contacts the top of the spool pin496; and the spool valve 421 and spool pin 496 mechanically secure theball check valve 492 in its seat area 497, thereby sealing the fluidpassage 476 from the vent line 494.

[0108] A displacement of the spool valve 421 to its lower, open positionterminates the fluid connection between the fluid path 476 and theannulus 475 and drain line 477. Further, displacement of the spool valve421 downward opens a fluid path via annulus 471 between the supplypassage 448 and the top of the fluid passage 476. Thus pressurizedhydraulic fluid from the cavity 470 is provided to fluid passage 476leading to the top of the intensifier piston 480 in the cavity 498. Theapplication of pressurized hydraulic fluid to the top of the intensifierpiston 480 forces the intensifier piston 480 downward in its cylinder orcavity 498. A plunger 500 operatively engages the intensifier piston 480to apply a very high pressure force on fuel within the cavity 502. Thepressure of the fuel entering the fuel injector 412 at inlet 429 may beabout 450 kPa or 65 psi. The intensifier piston 480 may increase thepressure of fuel within a nozzle cavity 504 to about 175 Mpa or 25,000psi as a function of the rail pressure. An inlet fill check valve 507prevents the high pressure fuel from flowing back out of the inlet port429. Of course, other fuel pressures are possible as well withoutdeparting from the spirit and scope of the present invention.

[0109] Opening the control passage 452 to the drain passage 450 alsoremoves the pressure of the hydraulic fluid over the check piston 486.As the pressure within the nozzle cavity 504 increases, a sufficientforce builds up on the end 506 of the nozzle check valve 488 to overcomethe force applied by the check piston return spring 508. The highlypressurized fuel in the nozzle cavity 504 effectively pushes the nozzlecheck valve 488 and the check piston 486 against the spring 508. The end506 of the nozzle check valve 488 is separated from its seat in the tip490, and highly pressurized fuel freely flows through the orifice ororifices 510 into the cylinder. The pilot injection phase continues aslong as the bender actuator 419 remains actuated; the spool valve 421remains open; and there is no pressurized hydraulic fluid on top of thecheck piston 486.

[0110] Subsequently, during the engine operation, an injection delayphase is initiated by the ECM 430 providing to the bender actuator 419 asecond command signal such as a DC biasing voltage of an oppositepolarity from the first command signal. The second command signal causesthe bender actuator 419 to move in a second direction opposite the firstdirection, such as a generally vertically upward direction. The benderactuator 419 moves to a more domed, quiescent prestressed, secondposition as shown in FIGS. 15A and 15B. As the bender actuator 419 movesupward, the return spring 456 moves the poppet 420 and actuating pin 454upward to a second position, such that the actuating pin 454 contactsthe center portion of the bender actuator 419.

[0111] Motion of the poppet 420 upward causes the second sealing area462 to engage the upper seat 464, thereby disconnecting the controlpassage 452 from the drain passage 450. Simultaneously, the firstannular sealing area 458 separates from the lower seal 460; andpressurized hydraulic fluid flows from the supply passage 448 to thecontrol passage 452. The reapplication of pressurized hydraulic fluid tothe control passage 452 creates a hydraulic force on top of the checkpiston 486. The check piston 486 and nozzle check valve are moveddownward until the end 506 engages the tip 490, thereby closing thenozzle check valve 488. With the nozzle check valve closed, the flow offuel from the output orifice 510 of the fuel injector 412 is terminated.Thus, injection of fuel into the cylinder is terminated immediatelyafter deactuating the bender actuator 419.

[0112] The application of pressurized hydraulic fluid to the controlpassage 452 again applies a hydraulic fluid force to the bottom 466 ofthe spool 421. That force in combination with a relatively weak force ofthe return spring 456 is slow to overcome the force of the pressurizedhydraulic fluid on the upper end 472 of the spool valve 421. Thus, thespool valve 421 is slow to move upward relative to the speed of closingof the nozzle check valve 488. During this period of initial slowoperation of the spool valve 421, pressurized hydraulic fluid continuesto flow past the spool valve 421 to the intensifier piston 480. With thenozzle check valve 488 closed and the continued application of ahydraulic force to the intensifier piston 480 and the plunger 500, thepiston 480 and plunger 500 continue to move downward. The continuedmovement of the intensifier piston 480 and plunger 500 again brings thefuel in the cavities 502 and 504 to the desired injection pressure inanticipation of the main injection phase. The duration of the injectiondelay phase is sufficiently small that the spool valve 421 never shutsoff the supply of pressurized hydraulic fluid to the top of theintensifier piston 480.

[0113] Subsequently, during the engine operation, the main injectionphase is initiated by the ECM 430 providing a third command signal toactuate the bender actuator 419. The third command signal is similar tothe first command signal that is described with respect to the pilotinjection phase. The third command signal is effective to cause thebender actuator 419 to move downward to its actuated, less domed, firstposition as illustrated in FIG. 16. The poppet valve 420 again changesstate and returns to its first position, thereby opening the controlpassage 452 to the drain passage 450. Pressure is immediately removedfrom the check piston 486, and the fuel in the cavity 504 that waspressurized during the delay cycle is effective to quickly open thenozzle check valve 488.

[0114] Simultaneously, removal of hydraulic pressure from the bottom 466of the spool valve 421 quickly opens the partially closed spool valve421, thereby applying full hydraulic fluid pressure to the top of theintensifier piston 480. The intensifier piston 480 and plunger 500continue their downward movement to maintain the desired injectionpressure on the fuel in the cavities 502, 504. The main injection phasecontinues for as long as the bender actuator 419 remains in its actuatedstate.

[0115] The main injection phase ends and the fill phase begins when theECM 430 provides a fourth command signal to the bender actuator 419. Thefourth command signal is similar to the second command signal and causesthe bender actuator 419 to move in the second, upward direction to itssecond, more domed, quiescent prestressed position as shown in FIG. 13A.Again, in a manner similar to that described with respect to the delayphase, the poppet valve 420 moves upward to its second position, therebyagain applying pressurized hydraulic fluid to the control passage 452and the top of the check piston 486. The check piston 486 movesdownward, thereby immediately closing the nozzle check valve 488 andterminating the flow of pressurized fuel through the orifice 510 of thefuel injector 412.

[0116] The pressurized hydraulic fluid in the control passage 452 alsoreestablishes a hydraulic force balance at the ends of the spool valve421, thereby permitting the return spring 474 to return the spool valve421 to its closed position. Closing the spool valve 421 terminates theflow of pressurized hydraulic fluid from the supply passage 448 to thefluid passage 476. Also, the fluid passage 476 is opened to the annulus475, so that hydraulic fluid pressure in the passage 476 is relievedthrough the drain 477. Further, as the spool valve raises away from thespool pin 496, the ball check valve 492 is able to release the pressureof the hydraulic fluid in the passage 476 via the vent 494.

[0117] As the pressurized hydraulic fluid is removed from the top of theintensifier piston 480, the return spring 482 pushes hydraulic fluid outof the cavity above the intensifier piston 480. The reverse check valve507 for the fuel inlet is lifted to its valve seat as the plunger 500 israised. This allows fuel to flow into the plunger cavity 502. The fillcycle is complete when the plunger 500 and intensifier piston 480 are attheir uppermost positions and the plunger cavity 502 is filled with fuelas shown in FIGS. 13A and 13B. At the end of the fill cycle, all of thecomponents of the fuel injector 412 are in respective states that definethe preinjection phase; and the fuel injector is ready for the next fuelinjection cycle.

[0118] While the use of hydraulic fluid is described herein, those ofordinary skill in the art will appreciate that other fluids may be usedas well, such as engine oil, fuel, transmission fluid, power steeringfluid, and engine coolant by way of example without departing from thespirit and scope of the present invention. Moreover, it will beunderstood that the check valve 488 may be caused to open and closeseveral times during an injection cycle so as to provide, for example,pilot, main and post injections.

[0119] With reference now to FIGS. 17-19, gasoline port injector 600 aand 600 b are shown in accordance with the principles of the presentinvention. Port injector 600 a includes a valve body 602 having an axialfluid passage 604 extending through the valve body 602 that communicatesbetween an inlet 606 and a fluid chamber 608 formed in the injector tip610. An elongated needle valve 612 is mounted to extend axially throughthe valve body 602 and includes a valve tip 614 that normally seats in avalve seat 616 to close a fluid orifice 618 formed at the remote end ofthe injector tip 610. The needle valve 612 is mounted for reciprocalmovement within the valve body 602 for selectively opening and closingthe orifice 618 during an injection cycle.

[0120] In accordance with one embodiment of the present invention, asshown in FIG. 17, the needle valve 602 is rigidly connected to at leastone piezoelectric device 622, such as a pre-stressed electroactivebender actuator, which may be thermally, mechanically or otherwiseprestressed, as described in detail above. The bender actuator 622 mayhave a cylindrical or disk configuration and may be coated with anelectrically insulating and/or otherwise protective material as is wellknown in the art.

[0121] Bender actuator 622 may comprise a plurality of benders actuators(configured in parallel or in series) that are individually stacked orbonded together into a single multi-layered element. While not shown,those of ordinary skill in the art will appreciate that multiple benderactuators 622 may be mounted in parallel within the valve body 602 toincrease the force applied by the bender actuators 622 to the needlevalve 612 in response to a control signal applied by the ECM (not shown)to the bender actuator 622 through electrical leads 624 (one shown).Alternatively, the bender actuators 622 may be mounted in series toincrease the stroke of the needle valve 612 upon axial displacement ofthe bender actuators 622 in response to the control signal. The benderactuator 622 is mounted within the valve body 602 by a clamping and loadring assembly, illustrated diagrammatically at 628, as described indetail above in connection with FIGS. 7A, 7B, 8 and 11.

[0122] As shown in FIG. 17, a cylindrical coupling member 628 extendsthrough a bore 630 formed through the center of the bender actuator 622and is fixed to the actuator 622 through a pair of locking collars 632that contact the major surfaces 634, 636 of the bender actuator 622 andmay be threaded, welded, glued or otherwise fastened to the couplingmember 628. One end of the coupling member 628 is operatively connectedto the needle valve 612 through a fastener (not shown) or any othersuitable means of attachment. Coupling member 628 includes an axialfluid passage 638 (FIG. 17) extending at least partially therethroughthat is in fluid communication with fluid passages 640 extending througha wall of the coupling member 628. The passages 638, 640 permit fuel topass from one side of the bender actuator 622 to the other side throughthe coupling member 628. As shown in FIG. 17, the needle valve 612 isconnected to the bender actuator 622 through the coupling member 628 sothat the needle valve 612 will travel axially within the valve body 602upon axial displacement of the bender actuator 622 from the domed, orunactuated configuration shown in FIG. 17 to a flattened, or actuatedposition (not shown).

[0123] In operation of the gasoline port 600 a of FIG. 17, the springrate of the bender actuator 622 is used to bias the needle valve 612 toa closed position so that the valve tip 614 seats in the valve seat 616to close the orifice 618. Fuel is delivered to the fluid chamber 608 inthe injector tip 610 through the axial fluid passage 604 and the fluidpassages 638, 640 that extend through the coupling member 628. During aninjection cycle, the ECM (not shown) applies a control signal to thebender actuator 622 that causes the bender actuator 622 to deform ordisplace axially by flattening out. As the bender actuator 622 flattensout in response to the control signal, the needle valve 612, by virtueof its rigid connection to the bender actuator 622, lifts off of thevalve seat 616 to open the orifice 618 for an injection of fuel. Afterthe injection cycle is complete, the control signal is eitherdiscontinued, or the polarity of the control signal is reversed, tocause the bender actuator 622 to return to its domed configuration asshown in FIG. 17.

[0124] A gasoline port injector 600 b in accordance with an alternativesecond embodiment of the present invention is shown in FIG. 18, wherelike numerals represent like parts to the gasoline port injector 600 aof FIG. 17. In this embodiment, the bender actuator 622 may have arectangular configuration as shown in FIG. 19, although otherconfigurations are possible as well. The bender actuator 622 includes apair of opposite minor sides 642 a and a pair of opposite major sides642 b. A hole 644 is provided in the center of bender actuator 622 topermit direct attachment of the needle valve 612 to the actuator 622through a suitable fastener (not shown) as described in detail above. Inthis embodiment, multiple fluid passages 646 communicate with the axialfluid passage 604 and are routed through the valve body 602 and aroundthe minor sides 642 a of the bender actuator 622. In this way, thecoupling member 628 for passing the fluid through the bender actuator622 may be eliminated.

[0125] Referring now to FIG. 20, a fluid metering valve 700 a inaccordance with one embodiment of the present invention is shown. Fluidmetering valve 700 a includes a plunger or piston 702 that is directlyconnected to a bender actuator 704 as described in detail above. Benderactuator 704 is supported by a support, shown diagrammatically at 706,that may comprise the clamping and load ring assembly described indetail above in connection with FIGS. 7A, 7B, 8 and 11. Bender actuator704 may have a cylindrical or disk configuration and include at leastone electroactive layer (not shown) positioned between a pair ofelectrodes (not shown), although other configurations are possible aswell without departing from the spirit and scope of the presentinvention. In a de-energized or static state, the bender actuator 704 ispreferably pre-stressed to have a domed configuration as shown in FIG.20.

[0126] When the electrodes (not shown) of the bender actuator 704 areenergized to place the bender actuator 704 in an actuated state, such aswhen a voltage or current control signal is applied by an actuatorcontrol system (not shown), the bender actuator 704 displaces axially byflattening out from the domed configuration. In particular, the benderactuator 704 displaces axially, i.e., flattens out, in one directionwhen it is actuated in response to a control signal of one polarity. Ina de-energized state, or in response to a control signal of an oppositepolarity, the bender actuator 704 displaces axially, i.e., returns toits domed configuration, in an opposite direction or the bender actuator704 may dome higher than its static state depending on the relayedcontrol signal. The bender actuator 704 is therefore bi-directional inits operation as described in detail above.

[0127] A portion of the plunger 702 extends into a fluid reservoirchamber 708 having a variable volume defined by a lower end 710 of theplunger 702 and an outlet check valve 712. A fluid inlet passage 714communicates with the fluid reservoir chamber 708 through an inlet checkvalve 716. The position of the lower end 710 of the plunger 702, andthus the volume of fluid in fluid reservoir chamber 708, may beaccurately calibrated or controlled by varying the voltage or currentapplied to the bender actuator 704. Additionally, the static position ofthe bender actuator 704, and thus the static volume of the fluidreservoir chamber 708, may be adjusted by varying the pre-load appliedto the bender actuator 704 through the clamping and load ring assembly,illustrated diagrammatically at 706.

[0128] Bender actuator 704 may comprise a plurality of bender actuators(configured in parallel or in series) that are individually stacked orbonded together into a single multi-layered element. While not shown,those of ordinary skill in the art will appreciate that multiple benderactuators 704 may be mounted in parallel to increase the force appliedby the bender actuators 704 to the plunger 702 in response to a controlsignal applied by the actuator control system (not shown).Alternatively, the bender actuators 704 may be mounted in series toincrease the stroke of the plunger 702 upon axial displacement of thebender actuators 704 in response to the control signal.

[0129] In operation, the fluid reservoir chamber 708 is filled withfluid through the fluid inlet passage 714 and the inlet check valve 716.During a fluid metering cycle, the bender actuator 704 is actuated by acontrol signal that causes the bender actuator 704 to displace axially,i.e., flatten out. The extent of the axial displacement, and thereforethe metering stroke of the piston or plunger 702, is accuratelycontrolled through the control signal applied to the bender actuator704. The plunger 702 can be accurately stroked to any position withinrange of motion of the bender actuator 704 in response to the appliedcontrol signal. As the plunger 702 displaces axially, the increasedpressure on the outlet check valve 712 causes the outlet check valve 712to open, thereby permitting a volume of fluid to be metered through thefluid metering valve 700 a. After a volume of fluid has been metered,the control signal is either discontinued, or the polarity of thecontrol signal is reversed, to cause the bender actuator 704 to returnto its domed configuration as shown in FIG. 20.

[0130] Referring now to FIG. 21, a fluid metering valve 700 b is shownin accordance with an alternative second embodiment of the presentinvention, where like numerals represent like parts to the fluidmetering valve 700 a of FIG. 20. In this embodiment, a plunger 718 isbiased into engagement with the bender actuator 704 through a biasingelement, such as return spring 720. It will be appreciated that biasingof the plunger 718 into engagement with the bender actuator 704 could beachieved through other mechanical or hydraulic means as well.

[0131] The plunger 718 engages the bender actuator 704 so that theplunger 718 will travel axially within the fluid reservoir chamber 708upon axial displacement of the bender actuator 704 from the domed, orunactuated configuration shown in FIG. 21 to a flattened, or actuatedposition (not shown) during a fluid metering cycle. After a fluidmetering cycle is complete, the control signal is either discontinued,or the polarity of the control signal is reversed, to cause the benderactuator 704 to return to its domed configuration as shown in FIG. 21.The return spring 720 returns the plunger 702 to its static position andmaintains engagement of the plunger 702 with the bender actuator 704.

[0132] Referring now to FIG. 22, a fluid metering valve 700 c is shownin accordance with an alternative third embodiment of the presentinvention, where like numerals represent like parts to the fluidmetering valve 700 a of FIG. 20. In this embodiment, the plunger 702 iseliminated so that the bender actuator 704 acts directly upon the fluidwithin fluid reservoir chamber 708 during a fluid metering cycle. Thefluid reservoir chamber 708 includes a sealed fluid chamber 722 that isformed beneath the bender actuator 704.

[0133] During a fluid metering cycle, the bender actuator 704 isactuated by a control signal that causes the bender actuator 704 todisplace axially, i.e., flatten out, and thereby increase the fluidpressure within fluid chambers 708 and 722. The extent of the axialdisplacement of the bender actuator 704, and therefore the increase influid pressure within the chambers 708 and 722, is accurately controlledthrough the control signal applied to the bender actuator 704. Theincreased pressure on the outlet check valve 712 causes the outlet checkvalve 712 to open, thereby permitting a volume of fluid to be meteredthrough the fluid metering valve 700 c. After a volume of fluid has beenmetered, the control signal is either discontinued, or the polarity ofthe control signal is reversed, to cause the bender actuator 704 toreturn to its domed configuration as shown in FIG. 22.

[0134] Referring now to FIG. 23, a fluid metering valve 700 d is shownin accordance with an alternative fourth embodiment of the presentinvention, where like numerals represent like parts to the fluidmetering valve 700 a of FIG. 20. In this embodiment, fluid meteringvalve 700 d includes an inlet fluid passage 724 and one or more outletfluid passages 726 (two shown) communicating with the inlet fluidpassage 724. A control valve 728 selectively seals the outlet fluidpassages 726 from the inlet fluid passage 724 when a closing head 730 ofthe control valve 728 engages a valve seat 732.

[0135] One end of the control valve 728 remote from the closing head 730is directly connected to the bender actuator 704 in a manner asdescribed in detail above. Other mountings of the bender actuator 704and the control valve 728 are possible as well without departing fromthe spirit and scope of the present invention. The control valve 728 ismounted for reciprocal movement for selectively opening and closing afluid passage between the inlet fluid passage 724 and the outlet fluidpassages 726 through bidirectional operation of the bender actuator 704.

[0136] In operation, a control signal of a predetermined magnitude isapplied to the bender actuator 704 for a predetermined duration of timeto cause the bender actuator 704 to displace axially, i.e., flatten out.The extent of the axial displacement of the closing head 730 from thevalve seat 732 is accurately controlled through the control signalapplied to the bender actuator 704 from an actuator control system (notshown). The actuator control system (not shown) may include aprogrammable timer to control the duration of time the control valve 728is held in the open position. A fluid pressure sensor (not shown) may beassociated with the inlet fluid passage 724 and coupled to the actuatorcontrol system (not shown) for monitoring the fluid pressure within theinlet fluid passage 724. Alternatively, the bender actuator 704 may beused as a pressure sensor so that the bender actuator 704 has a voltageor current output that is generally proportional to the fluid pressurewithin the inlet fluid passage 724.

[0137] The actuator control system (not shown) is programmed to open thecontrol valve 728 so that a predetermined volume of fluid is meteredthrough the outlet fluid passages 726. As those of ordinary skill in theart will appreciate, the metered volume of fluid is determined by thefluid pressure within the inlet fluid passage 724 and the duration timethe control valve 728 is opened by the bender actuator 704.

[0138] Referring now to FIG. 24, a relief or reducing valve 800 inaccordance with the principles of the present invention is shown. Inthis embodiment, relief or reducing valve 800 includes an inlet fluidpassage 802 communicating with a pressurized fluid system 804, and oneor more outlet fluid passages 806 (two shown). A control valve 808selectively seals the outlet fluid passages 806 from the inlet fluidpassage 802 when a closing head 810 of the control valve 808 engages avalve seat 812. The closing head 810 of the relief or reducing valve 800could be an angled seat type, flat seat type, needle valve type, spoolvalve type, poppet valve type, or other valve type known to those ofskill in the art.

[0139] One end of the control valve 808 remote from the closing head 810is directly connected to a bender actuator 814 in a manner as describedin detail above. Other mountings of the bender actuator 814 and controlvalve 808 are possible as well without departing from the spirit andscope of the present invention. The control valve 808 is mounted forreciprocal movement for selectively opening and closing a fluid passagebetween the inlet fluid passage 802 and the outlet fluid passages 806through bidirectional operation of the bender actuator 814. As will bedescribed in detail below, in one embodiment where the control valve 808is a relief valve, the control valve 808 is selectively opened to avoidpressure extremes in the pressurized system 804. Alternatively, in oneembodiment where the control valve 808 is a reducing valve, the controlvalve 808 is selectively opened to provide a reduced fluid pressure inthe outlet fluid passages 806, such as for use in brake systems,differential locks, power-take-off clutches and other systems requiringa controlled fluid pressure within the system.

[0140] In operation, the bender actuator 814 may be used as a pressuresensor so that the bender actuator 814 has a voltage or current outputthat is generally proportional to the fluid pressure within the inletfluid passage 802 and the pressurized system 804. Alternatively, aseparate pressure sensor (not shown) could be used. An actuator controlsystem (not shown) receives the pressure information from the benderactuator 814 or a separate fluid pressure sensor (not shown) and opensthe control valve 808 through a control signal of predeterminedmagnitude so that either extreme pressures in the pressurized system 804are avoided or, alternatively, the fluid pressure in the outlet fluidpassages 806 is reduced to a predetermined pressure. In one embodimentwhere the control valve 808 is a relief valve, after the fluid pressureis relieved, the control signal is either discontinued, or the polarityof the control signal is reversed, to cause the bender actuator 814 toreturn to its domed configuration as shown in FIG. 24 to seat theclosing head 810 on the valve seat 812. In one embodiment where thecontrol valve 808 is a reducing valve, the control signal is adjusted toopen or restrict the fluid passage between the inlet fluid passage 802and the outlet fluid passages 806 to maintain the desired fluid pressurein the outlet fluid passages 806.

[0141] Referring now to FIG. 25, a direct valve 900 in the form of apiezoelectric device, such as a bender actuator 902 as described indetail above, is provided to selectively open and close a fluid aperture904. The bender actuator 902 is supported in a support, showndiagrammatically at 906, that forms a fluid seal about the entireperiphery of the bender actuator 902. The bender actuator 902 and thefluid seal around the entire periphery of the actuator 902 form a fluidchamber 908 that communicates with the fluid aperture 904 and fluidpassages 910. Additional fluid apertures (not shown) may communicatewith the fluid chamber 908.

[0142] The bender actuator 902 may have a cylindrical or diskconfiguration and may be coated with an electrically insulating and/orotherwise protective material as well known in the art.

[0143] In a de-energized or static state, the bender actuator 902 ispreferably pre-stressed to have a domed configuration as shown in FIG.25 so that the fluid aperture 904 is opened. When the electrodes (notshown) of the bender actuator 902 are energized to place the benderactuator 902 in an actuated state, such as when a voltage or currentcontrol signal is applied by an actuator control system (not shown), thebender actuator 902 displaces axially by flattening out from the domedconfiguration to directly seal with the fluid aperture 904 to preventthe flow of fluid from the fluid chamber 908 to the fluid passages 910.Of course, the orientation and operation of the bender actuator 902could be changed so that the bender actuator 902 directly seals thefluid aperture 904 in its static, or unactuated state, and opens thefluid aperture 904 in its actuated state.

[0144] With reference now to FIGS. 26-27, direct-injection gasolineinjectors 1000 a and 1000 b are shown in accordance with the principlesof the present invention. Injector 1000 a includes a valve body 1002having an axial fluid passage 1004 and multiple fluid passages 1006extending through the valve body 1002 that communicate between an inlet1008 and a fluid chamber 1010 formed in the injector tip 1012. Anoutwardly opening, elongated check valve 1014 is mounted to extendaxially through the valve body 1012 and includes a closing head 1016that normally seats in a conically-shaped valve seat 1018 to close afluid orifice 1020 formed at the remote end of the injector tip 1012.The check valve 1014 is biased to the closed position by a biasingelement, such as by a return spring 1022, that acts on an annular flange1024 extending radially outwardly from the check valve 1014. The annularflange 1024 includes multiple apertures 1026 that permit fluid flow fromthe axial fluid passage 1004 to the fluid chamber 1010. While not shown,it will be appreciated in an alternative embodiment that the fluid maybe diverted around the annular flange 1024 through one or more fluidpassages formed in the valve body 1002 (not shown). The check valve 1014is mounted for reciprocal movement within the valve body 1002 forselectively opening and closing the orifice 1020 during an injectioncycle.

[0145] In the embodiment of FIG. 26, one end of the check valve 1014remote from the closing head 1016 engages at least one bender actuator1028, such as a pre-stressed electroactive bender actuator, which may bethermally, mechanically or otherwise prestressed, as described in detailabove. The check valve 1014 engages the bender actuator 1028 so that thecheck valve 1014 will travel axially within the valve body 1002 uponaxial displacement of the bender actuator 1028 from the domed, orunactuated configuration shown in FIG. 26 to a flattened, or actuatedposition (not shown).

[0146] The bender actuator 1028 may have a rectangular configuration asshown in FIG. 19, although other configurations are possible as well.The bender actuator 1028 may be coated with an electrically insulatingand/or otherwise protective material as well known in the art. Benderactuator 1028 may comprise a plurality of bender actuators (configuredin parallel or in series) that are individually stacked or bondedtogether into a single multi-layered element. While not shown, those ofordinary skill in the art will appreciate that multiple bender actuators1028 may be mounted in parallel within the valve body 1002 to increasethe force applied by the bender actuators 1028 to the check valve 1014in response to a control signal applied by the ECM (not shown) throughelectrical leads 1030 (one shown). Alternatively, the bender actuators1028 may be mounted in series to increase the stroke of the check valve1014 upon axial displacement of the bender actuators 1028 in response tothe control signal. The bender actuator 1028 is mounted within the valvebody 1002 by a clamping and load ring assembly, illustrateddiagrammatically at 1032, as described in detail above in connectionwith FIGS. 7A, 7B, 8 and 11.

[0147] In operation of the direct-injection gasoline injector 1000 a ofFIG. 26, the return spring 1022 biases the outwardly opening check valve1014 to a closed position so that the closing head 1016 seats in theconically-shaped valve seat 1018 to close the orifice 1020. Fuel isdelivered to the chamber 1010 through the axial fluid passage 1004 andthe multiple apertures 1026 formed in the annular flange 1024. During aninjection cycle, the ECM (not shown) applies a control signal to thebender actuator 1028 that causes the bender actuator 1028 to deform ordisplace axially by flattening out. As the bender actuator 1028 flattensout in response to the control signal, the check valve 1014, by virtueof its engagement with the bender actuator 1028, is pushed off of theconically-shaped valve seat 1018 against the force of return spring 1022to open the orifice 1020 for an injection of fuel. After the injectioncycle is complete, the control signal is either discontinued, or thepolarity of the control signal is reversed, to cause the bender actuator1028 to return to its domed configuration as shown in FIG. 26. Thereturn spring 1022 assists in returning the check valve 1014 to itsclosed position so that the closing head 1016 engages theconically-shaped valve seat 1018 to seal the orifice 1020.

[0148] Referring now to FIG. 27, a direct-injection gasoline injector1000 b in accordance with an alternative second embodiment of thepresent invention is shown, where like numerals represent like parts tothe gasoline injector 1000 a of FIG. 26. In this embodiment, theelongated check valve 1014 is rigidly connected to the bender actuator1028 in a manner as described in detail above so that the bi-directionaloperation of the bender actuator 1028 is used to move the check valve1014 to both its open and closed positions. The rigid connection of thecheck valve 1014 to the bender actuator 1028 permits the return spring1022 to be eliminated so that the bender actuator 1028 provides thenecessary force to return the check valve 1014 to its closed position.As described in detail above, the spring rate of the bender actuator1028 may be adjusted by the clamping and load ring assembly 1032 topre-load the check valve 1014 against the conically-shaped valve seat1018.

[0149] Industrial Applicability

[0150] The common rail fuel injectors 100 a-100 e of the presentinvention have many advantages over common rail fuel injectors of theprior art. In each of the embodiments of FIGS. 1-4, the bender actuator122 directly controls the opening and closing of the elongated needlevalve 110 and check valve 138. Therefore, the hydraulic control chambernormally associated with common rail fuel injectors is eliminated. Thisremoves a source of variability in the operation of the common rail fuelinjectors 100 a-100 d, and results in more precise and accurate controlover fuel metering during an injection cycle. In the common rail fuelinjector 100 e, the bender actuator 122 directly controls the openingand closing of the control valve 170 to selectively communicate thecontrol fluid chamber 156 to the drain 171. This results in a moreprecise and accurate control over fuel metering during an injectioncycle than provided by solenoid, piezoelectric stack ormagnetorestrictive rod actuated control valves found in common rail fuelinjectors of the prior art.

[0151] The improved electrohydraulic actuator 310 of the presentinvention uses a bender actuator 312 as a mechanical power source. Thebender actuator 312 is physically small, uses little power, has veryfast response times and has a proportionally controllable bidirectionaloperation. Thus, the electrohydraulic actuator 310 is relatively small,has great flexibility, and is power efficient.

[0152] Further, the use of a bender actuator 312 in the electrohydraulicactuator 310 provides significant advantages over electromagneticsolenoids. First, the small mass and low inertia of a bender actuator312 provides it with extremely fast response times, such asapproximately 150 microseconds. The fast response time allows for a veryfast switching time of the poppet 330 as well as the device 315. Thus,the very fast response time of the electrohydraulic actuator 310 permitsthe electrohydraulic actuator 310 to be used in a wide range ofapplications.

[0153] The bender actuator 312 has a further advantage of having acapability of proportional bidirectional operation. Thus, the poppet 330can be moved in both directions by means of different such as positiveand negative command signals. This allows for either the elimination ofa return spring 346 or the use of a substantially smaller return spring346. In addition, the capability of proportional bidirectional controlprovides an electrohydraulic actuator 310 that has the capability ofadjusting the velocity of the poppet 330 and the valve 314 hydraulicallyconnected to the poppet 330.

[0154] The bender actuator 312 has a still further advantage in that itdraws considerably less power than an electromagnetic solenoid. Further,due to its capacitive behavior, a bender actuator 312 draws no powerduring a “hold-in” period where actuation is maintained for a relativelylong period of time.

[0155] In addition, multiple bender actuators 312 may be easily combinedin a stacked, parallel manner to provide a force that is approximatelylinearly related to the number of actuators in the stack. In addition,the actuators may be combined in a serial manner to increase themagnitude of the stroke, that is, the displacement. Even in a stackedarrangement, actuators are relatively small and may take up less spacethan electromagnetic solenoids and piezoelectric stacks.

[0156] The fuel injector 412 of the present invention provides manyadvantages over solenoid-controlled fuel injectors of the prior art. Forexample, it is often difficult to accurately control movement ofsolenoid-controlled fuel injector valves through control signals appliedto the solenoid, especially when intermediate positioning of thesolenoid-controlled valve is desired such as in operation of the poppetand spool valves, 420 and 421, respectively. Factors such as inductivedelays, eddy currents and variability in components (i.e., springpreloads, solenoid force characteristics and varying fluid flow forces)must all be considered and accounted for in a solenoid-controlled fuelinjector design. Further, the response time of solenoids limits theminimum possible dwell times between multiple injection events and makesthe fuel injector generally more susceptible to various sources ofvariability. Additionally, components of a solenoid generally increasethe overall mass and power requirements of a solenoid-controlled fuelinjector system.

[0157] The prestressed bender actuator 419 of the present inventioneliminates the drawbacks of known solenoid-controlled valves byproviding rapid, accurate, and repeatable controlled movement of thepoppet and spool valves, 420 and 421, respectively, between their open,partially open and closed positions. The bender actuator 419 of thepresent invention is a generally lightweight, proportional device havinga stroke output that is proportional to the input control signal.Accurate, repeatable bidirectional movement of the poppet and spoolvalves, 420 and 421, respectively, is controlled simply by varying themagnitude and polarity of the control signal applied to the benderactuator 419. Further, the bender actuator 419 of the present inventionhas a fast response time so that dwell time between multiple injectionevents can be reduced, thereby also reducing variability from injectionevent to injection event. Additionally, prestressed bender actuator 419acts as a capacitive load and will remain in its actuated position for aperiod of time after the ECM control signal is terminated unlike asolenoid that requires a continuous voltage signal during its actuationphase. Therefore, the fuel injector 412 of the present invention isgenerally lighter and requires less power for operation thansolenoid-controlled fuel injectors of the past.

[0158] Gasoline port injectors 600 a and 600 b have the advantage thatthe needle valve 612 used to open and close the fluid orifice 618 iscontrolled by the pre-stressed bender actuator 622 having all of theadvantages described in detail above in connection with bender actuators312 and 419.

[0159] In the fluid metering valves 700 a and 700 b, the bender actuator704 provides very accurate and repeatable bidirectional movement of theplungers 702 and 718 in the fluid reservoir chambers 708 to provideprecise metering of fluid from the outlet check valves 712.

[0160] In the fluid metering valve 700 c, the axial movement of thebender actuator 704 is accurately controlled to increase the fluidpressure in the fluid reservoir chamber 708 and sealed fluid chamber722. The increase in fluid pressure is accurately controlled to meter avolume of fluid through the outlet check valve 712.

[0161] In the fluid metering valve 700 d, the bender actuator 704 isused to control the position of control valve 728 relative to the valveseat 732. The programmable timer coupled to the actuator control systemcontrols the duration of time the control valve 728 is opened, while thefluid pressure sensor associated with the inlet fluid passage 724 andcoupled to the actuator control system monitors the fluid pressurewithin the inlet fluid passage 724. The volume of fluid metered by themetering valve 700 d is determined by the fluid pressure within theinlet fluid passage 724 and the duration of time the control valve 728is opened by the bender actuator 704.

[0162] In the relief or reducing valve 800, the bender actuator 814 isused to control the position of control valve 808. Control valve 808controls communication of the inlet fluid passage 802 and the outletfluid passages 806. In one embodiment, where the control valve 808 is arelief valve, the control valve 808 is selectively opened to avoidpressure extremes in the pressurized system 804. Alternatively, in oneembodiment where the control valve 808 is a reducing valve, the controlvalve 808 is selectively opened to provide a reduced fluid pressure inthe outlet fluid passages 806.

[0163] In the direct valve 900, the bender actuator 902 is use toselectively open and close fluid aperture 904. In a de-energized orstatic state, the bender actuator 902 is preferably pre-stressed to havea domed configuration is shown in FIG. 25 so that the fluid aperture 904is opened. When the electrodes (not shown) of the bender actuator 902are energized to place the bender actuator 902 in an actuated state,such as when a voltage or current control signal is applied by anactuator control system (not shown), the bender actuator 902 displacesaxially by flattening out from the domed configuration to directly sealwith the fluid aperture 904 to prevent the flow of fluid from the fluidchamber 908 to the fluid passages 910.

[0164] Direct-injection gasoline injectors 1000 a and 1000 b have theadvantage that the check valve 612 used to open and close the fluidorifice 1020 is controlled by the pre-stressed bender actuator 1028having all of the advantages described in detail above in connectionwith bender actuators 312 and 419.

[0165] While the present invention has been illustrated by a descriptionof various embodiments, and while these embodiments have been describedin considerable detail, it is not the intention of Applicants torestrict or in any way limit the scope of the appended claims to suchdetail. Additional advantages and modifications will readily appear tothose skilled in the art. The invention in its broader aspects is,therefore, not limited to the specific details, representative apparatusand method, and illustrative example shown and described. Accordingly,departures may be made from such details without departing from thespirit or scope of Applicants' general inventive concept.

What is claimed is:
 1. A valve system, comprising: a valve body; a fluidchamber disposed within said valve body and adapted to communicate witha fluid source for containing fluid therein; a fluid orificecommunicating with said fluid chamber; a valve member mounted withinsaid valve body and movable between a closed position for closing saidfluid orifice and an open position for opening said fluid orifice; and apre-stressed bender actuator operatively engaging said valve member andoperable to selectively move said valve member to at least one of saidclosed and open positions to close and open said fluid orifice.
 2. Thevalve system of claim 1, wherein said valve member is rigidly connectedto said bender actuator so that said bender actuator is operable to movesaid valve member to said closed and open positions.
 3. The valve systemof claim 1 further comprising a biasing element operatively engagingsaid valve member and operable to effectively bias said valve member tosaid closed position for closing said fluid orifice.
 4. The valve systemof claim 3, wherein said valve member includes a radially outwardlydirected flange, said biasing element operatively engaging said radiallyoutwardly directed flange and operable to effectively bias said valvemember to said closed position for closing said fluid orifice.
 5. Thevalve system of claim 1, wherein said bender actuator has a domedconfiguration that effectively moves said valve member to said closedposition in a static state of said bender actuator for closing saidfluid orifice.
 6. The valve system of claim 5, wherein said benderactuator is operable to displace axially in an actuated state of saidbender actuator to effectively move said valve member to said openposition for opening said fluid orifice.
 7. The valve system of claim 1,wherein said fluid chamber is adapted to communicate with a pressurizedfluid source.
 8. The valve system of claim 1, wherein said valve systemcomprises a common rail fuel injector.
 9. The valve system of claim 1,wherein said valve member comprises a needle valve.
 10. The valve systemof claim 1, wherein said valve member comprises an outwardly openingcheck valve.
 11. The valve system of claim 1 further comprising asupport device mounted within said valve body operable to support saidbender actuator and selectively vary a preload of said bender actuator.12. The valve system of claim 11 wherein at least a portion of saidsupport device threadably engages a portion of said valve body.
 13. Avalve system, comprising: a valve body; a fluid chamber disposed withinsaid valve body and adapted to communicate with a fluid source forcontaining fluid therein; a fluid orifice communicating with said fluidchamber; a control fluid chamber disposed within said valve body andadapted to communicate with a fluid source for containing fluid thereinand selectively to a drain for draining fluid from said control fluidchamber; a valve member mounted within said valve body and movablebetween a closed position for closing said fluid orifice and an openposition for opening said fluid orifice, said valve member movingbetween said closed and open positions in response to a difference influid pressure in said fluid chamber and said control fluid chamber; acontrol valve member mounted within said valve body and operable to movebetween a closed position for containing fluid within said control fluidchamber and an open position for draining fluid from said control fluidchamber; and a pre-stressed bender actuator operatively engaging saidcontrol valve member and operable to selectively move said control valvemember to at least one of said closed and open positions.
 14. The valvesystem of claim 13, wherein said control valve member is rigidlyconnected to said bender actuator so that said bender actuator isoperable to move said control valve member to said closed and openpositions.
 15. The valve system of claim 13 further comprising a biasingelement operatively engaging said control valve member and operable toeffectively bias said control valve member to said closed position forcontaining fluid within said control fluid chamber.
 16. The valve systemof claim 13, wherein said bender actuator has a domed configuration thateffectively moves said control valve member to said closed position in astatic state of said bender actuator for containing fluid within saidcontrol fluid chamber.
 17. The valve system of claim 16, wherein saidbender actuator is operable to displace axially in an actuated state ofsaid bender actuator to effectively move said control valve member tosaid open position for draining fluid from said control fluid chamber.18. The valve system of claim 13 further comprising a biasing elementoperatively engaging said valve member and operable to effectively biassaid valve member to said closed position for closing said fluidorifice.
 19. The valve system of claim 13, wherein said fluid chamber isadapted to communicate with a pressurized fluid source.
 20. The valvesystem of claim 13, wherein said control fluid chamber is adapted tocommunicate with a pressurized fluid source.
 21. The valve system ofclaim 13, wherein said valve system comprises a common rail fuelinjector.
 22. An apparatus for adjusting a preload of a piezoelectricdevice having first and second opposed surfaces and a peripheral edgeextending therebetween, comprising: a clamping device configured toengage the first and second opposed surfaces of the piezoelectric deviceproximate the peripheral edge and operable to apply a variable clampingforce to the piezoelectric device; and a load device operativelyengaging said clamping device and operable to vary the applied clampingforce to adjust the preload of the piezoelectric device.
 23. Theapparatus of claim 22 wherein the clamping device comprises: a firstclamping member operable to engage the first surface of thepiezoelectric device; and a second clamping member mounted for movementrelative to the first clamping member and operable to engage the secondsurface of the piezoelectric device.
 24. The apparatus of claim 23wherein the first clamping member comprises: a first upstanding walladapted to surround at least a portion of the peripheral edge of thepiezoelectric device; and a first support flange extending from thefirst upstanding wall and adapted to engage the first surface of thepiezoelectric device proximate the peripheral edge.
 25. The apparatus ofclaim 24 wherein the second clamping member comprises: a secondupstanding wall positioned adjacent the first upstanding wall of thefirst clamping member and adapted to engage the second surface of thepiezoelectric device proximate the peripheral edge.
 26. The apparatus ofclaim 25 wherein the load device operatively engages one of the firstand second clamping members for moving one of the first and secondclamping members relative to the other.
 27. The apparatus of claim 22,wherein said first clamping member comprises a generally annular ring.28. The apparatus of claim 27, wherein said second clamping membercomprises a generally annular ring.
 29. The apparatus of claim 28,wherein said load device comprises a generally annular ring.
 30. Anapparatus for adjusting a preload of a piezoelectric device having firstand second opposed surfaces and a peripheral edge extendingtherebetween, comprising: a housing; a cavity disposed in said housingand having upstanding walls defining said cavity; a clamping devicemounted in said cavity and configured to engage the first and secondopposed surfaces of the piezoelectric device proximate the peripheraledge and operable to apply a variable clamping force to thepiezoelectric device; and a load device mounted in said cavity andoperatively engaging said walls of said cavity, said load deviceoperatively engaging said clamping device and being operable to vary theapplied clamping force to adjust the preload of the piezoelectricdevice.
 31. The apparatus of claim 30, wherein said load devicethreadably engages said walls of said cavity.
 32. The apparatus of claim30 wherein the clamping device comprises: a first clamping memberoperable to engage the first surface of the piezoelectric device; and asecond clamping member mounted for movement relative to the firstclamping member and operable to engage the second surface of thepiezoelectric device.
 33. The apparatus of claim 32 wherein the firstclamping member comprises: a first upstanding wall adapted to surroundat least a portion of the peripheral edge of the piezoelectric device;and a first support flange extending from the first upstanding wall andadapted to engage the first surface of the piezoelectric deviceproximate the peripheral edge.
 34. The apparatus of claim 33 wherein thesecond clamping member comprises: a second upstanding wall positionedadjacent the first upstanding wall of the first clamping member andadapted to engage the second surface of the piezoelectric deviceproximate the peripheral edge.
 35. The apparatus of claim 34 wherein theload device operatively engages one of the first and second clampingmembers for moving one of the first and second clamping members relativeto the other.
 36. The apparatus of claim 30, wherein said first clampingmember comprises a generally annular ring.
 37. The apparatus of claim30, wherein said second clamping member comprises a generally annularring.
 38. The apparatus of claim 30, wherein said load device comprisesa generally annular ring.
 39. A method for adjusting a preload of apiezoelectric device having first and second opposed surfaces and aperipheral edge extending therebetween, comprising: clamping thepiezoelectric device by engaging the opposed first and second surfacesof the piezoelectric device proximate the peripheral edge; applying aclamping force to the piezoelectric device; and varying the appliedclamping force to vary the preload of the piezoelectric device.
 40. Amethod for adjusting a preload of a piezoelectric device having firstand second opposed surfaces and a peripheral edge extendingtherebetween, comprising: engaging the first surface of thepiezoelectric device with a first clamping member; engaging the secondsurface of the piezoelectric device with a second clamping member; andmoving the first and second clamping members relative to each other toapply a clamping force to the piezoelectric device that varies thepreload of the piezoelectric device.
 41. The method of claim 40 whereinengaging the first surface of the piezoelectric device comprisesengaging the first surface of the piezoelectric device with the firstclamping member proximate the peripheral edge.
 42. The method of claim40 wherein engaging the second surface of the piezoelectric devicecomprises engaging the second surface of the piezoelectric device withthe second clamping member proximate the peripheral edge.
 43. A valvesystem, comprising: a valve body having a fluid inlet adapted tocommunicate with a fluid source and a fluid outlet adapted to emitfluid; a fluid passageway extending through said valve body between saidfluid inlet and said fluid outlet; a valve member mounted at leastpartially in said fluid passageway and movable between a closed positionfor closing said fluid orifice and an open position for opening saidfluid orifice; and a pre-stressed bender actuator operatively engagingsaid valve member and operable to selectively move said valve member toat least one of said closed and open positions to close and open saidfluid orifice.
 44. The valve system of claim 43, wherein said valvemember is rigidly connected to said bender actuator so that said benderactuator is operable to move said valve member to said closed and openpositions.
 45. The valve system of claim 43 further comprising a biasingelement operatively engaging said valve member and operable toeffectively bias said valve member to said closed position for closingsaid fluid orifice.
 46. The valve system of claim 45, wherein said valvemember includes a radially outwardly directed flange, said biasingelement operatively engaging said radially outwardly directed flange andoperable to effectively bias said valve member to said closed positionfor closing said fluid orifice.
 47. The valve system of claim 43,wherein said bender actuator has a domed configuration that effectivelymoves said valve member to said closed position in a static state ofsaid bender actuator for closing said fluid orifice.
 48. The valvesystem of claim 47, wherein said bender actuator is operable to displaceaxially in an actuated state of said bender actuator to effectively movesaid valve member to said open position for opening said fluid orifice.49. The valve system of claim 43, wherein said valve system comprises agasoline port injector.
 50. The valve system of claim 43, wherein saidvalve system comprises a direct-injection gasoline injector.
 51. Thevalve system of claim 43, wherein said valve member comprises a needlevalve.
 52. The valve system of claim 43, wherein said valve membercomprises an outwardly opening check valve.
 53. The valve system ofclaim 43 further comprising a support device mounted within said valvebody operable to support said bender actuator and selectively vary apreload of said bender actuator.
 54. The valve system of claim 53wherein at least a portion of said support device threadably engages aportion of said valve body.
 55. The valve system of claim 43 furthercomprising a coupling member operatively connecting said valve memberand said bender actuator.
 56. The valve system of claim 55, wherein saidcoupling member includes a fluid passage in communication with saidfluid passage in said valve body.
 57. The valve system of claim 56,wherein said fluid passage of said coupling member extends through saidbender actuator.
 58. A fluid metering valve, comprising: a fluidreservoir chamber adapted to communicate with a fluid source forcontaining fluid therein; a fluid outlet communicating with said fluidreservoir chamber; a plunger member mounted for selective movement insaid fluid reservoir chamber and operable to meter a volume of fluidfrom said fluid orifice upon movement of said plunger member toward saidfluid outlet; and a pre-stressed bender actuator operatively engagingsaid plunger member and operable to selective move said plunger membertoward said fluid outlet to meter a volume of fluid.
 59. The fluidmetering valve of claim 59, wherein said plunger member is rigidlyconnected to said bender actuator so that said bender actuator isoperable to move said valve member toward and away from said fluidoutlet.
 60. The fluid metering valve of claim 58 further comprising abiasing element operatively engaging said plunger member and operable toeffectively bias said plunger member into engagement with said benderactuator.
 61. The fluid metering valve of claim 58, wherein said benderactuator has a domed configuration in a static state of said benderactuator.
 62. The fluid metering valve of claim 61, wherein said benderactuator is operable to displace axially in an actuated state of saidbender actuator to selectively move said plunger member in said fluidreservoir chamber to meter a volume of fluid from said fluid orifice.63. A fluid metering valve, comprising: a fluid reservoir chamberadapted to communicate with a fluid source for containing fluid therein;a fluid outlet communicating with said fluid reservoir chamber; and apre-stressed bender actuator operable to act directly on the fluidcontained in said fluid reservoir chamber so that a volume of fluid ismetered from said fluid outlet upon actuation of said bender actuatortoward said fluid outlet.
 64. The fluid metering valve of claim 63,wherein said bender actuator has a domed configuration in a static stateof said bender actuator.
 65. The fluid metering valve of claim 64,wherein said bender actuator is operable to displace axially in anactuated state of said bender actuator toward said fluid outlet to meterthe volume of fluid from said fluid outlet.
 66. A fluid metering valve,comprising: a inlet fluid passage adapted to communicate with a fluidsource for carrying fluid therein; an outlet fluid passage communicatingwith said inlet fluid passage; a valve seat disposed at a juncture ofsaid inlet fluid passage and said outlet fluid passage; a valve membermounted for selective movement relative to said valve seat between aclosed position for closing fluid communication between said inlet fluidpassage and said outlet fluid passage and an open position for openingfluid communication between said inlet fluid passage and said outletfluid passage to meter a volume of fluid through the outlet fluidpassage; and a pre-stressed bender actuator operatively engaging saidvalve member and operable to selective move said valve member to atleast one of said open and closed positions.
 67. The fluid meteringvalve of claim 66, wherein said valve member is rigidly connected tosaid bender actuator so that said bender actuator is operable to movesaid valve member to said closed and open positions.
 68. The fluidmetering valve of claim 66, wherein said bender actuator has a domedconfiguration in a static state of said bender actuator.
 69. The fluidmetering valve of claim 66, wherein said bender actuator is operable todisplace axially in an actuated state of said bender actuator to movesaid valve member to said open position.
 70. The fluid metering valve ofclaim 66, further comprising a pressure sensor operable to detect afluid pressure in said inlet fluid passage.
 71. The fluid metering valveof claim 70, wherein said bender actuator comprises said pressuresensor.
 72. A fluid metering valve, comprising: an inlet fluid passageadapted to communicate with a pressurized fluid source for carryingpressurized fluid therein; a pressure sensor operable to detect a fluidpressure in said inlet fluid passage; an outlet fluid passagecommunicating with said inlet fluid passage; a valve seat disposed at ajuncture of said inlet fluid passage and said outlet fluid passage; avalve member mounted for selective movement relative to said valve seatbetween a closed position for closing fluid communication between saidinlet fluid passage and said outlet fluid passage and an open positionfor opening fluid communication between said inlet fluid passage andsaid outlet fluid passage to regulate a fluid pressure in said inletfluid passage; and a pre-stressed bender actuator operatively engagingsaid valve member and operable to selective move said valve member to atleast one of said open and closed positions in response a detected fluidpressure in said inlet fluid passage by said pressure sensor.
 73. Thefluid metering valve of claim 72, wherein said valve member is rigidlyconnected to said bender actuator so that said bender actuator isoperable to move said valve member to said closed and open positions.74. The fluid metering valve of claim 72, wherein said bender actuatorhas a domed configuration in a static state of said bender actuator. 75.The fluid metering valve of claim 72, wherein said bender actuator isoperable to displace axially in an actuated state of said benderactuator to move said valve member to said open position.
 76. The fluidmetering valve of claim 75, wherein said bender actuator comprises saidpressure sensor.
 77. The fluid metering valve of claim 72, wherein saidfluid metering valve comprises one of a reducing valve and a reliefvalve.
 78. A valve system, comprising: a fluid chamber; a fluid passagecommunicating with said fluid chamber; a fluid aperture disposed at ajuncture of said fluid chamber and said fluid passage; and apre-stressed bender actuator operable to act directly on said fluidaperture between a closed position for closing fluid communicationbetween said fluid chamber and said fluid passage and an open positionfor opening fluid communication between said fluid chamber and saidfluid passage.
 79. The valve system of claim 78, wherein said benderactuator has a domed configuration in a static state of said benderactuator for spacing said bender actuator away from said fluid apertureto thereby open fluid communication between said fluid chamber and saidfluid passage.
 80. The valve of claim 78, wherein said bender actuatoris operable to displace axially in an actuated state of said benderactuator to move into direct engagement with said fluid aperture tothereby close fluid communication between said fluid chamber and saidfluid passage.
 81. An apparatus comprising: a prestressed electroactivebender actuator operable to receive a command signal and operable tomove between first and second positions as a function of the commandsignal; and a valve coupled with the prestressed electroactive benderactuator, the valve being operated in response to the prestressedelectroactive bender actuator moving between the first and secondpositions.
 82. The apparatus of claim 1 wherein the valve opens andcloses as a function of the prestressed bender actuator moving betweenthe first and second positions.
 83. The apparatus of claim 2 wherein thevalve is adapted to be fluidly coupled to a pressurized fluid source,and the valve provides a flow of pressurized fluid representing a firststate in response to the prestressed electroactive bender actuatormoving from the first position to the second position, and the valveterminates the flow of the pressurized fluid representing a second statein response to the prestressed electroactive bender actuator moving fromthe second position to the first position.
 84. The apparatus of claim 1wherein the valve is mechanically coupled with the prestressedelectroactive bender actuator and the valve is moved by the prestressedelectroactive bender actuator moving between the first and secondpositions.
 85. The apparatus of claim 4 wherein the prestressedelectroactive bender actuator moves through a displacement in a firstdirection in response to a first command signal, and the valve is movedin the first direction to an open position, thereby providing a supplyof pressurized fluid.
 86. The apparatus of claim 5 wherein theprestressed electroactive bender actuator moves through a displacementin an opposite direction in response to a second command signal, and thevalve is moved in the opposite direction to a closed position, therebyterminating the supply of the pressurized fluid.
 87. A method ofoperating a device in response to a command signal comprising: applyingthe command signal to a prestressed electroactive bender actuator;switching the prestressed electroactive bender actuator between firstand second operating states as a function of the command signal; andswitching a valve between first and second operating states as afunction of the prestressed electroactive bender actuator switchingbetween the first and the second operating states, the valve operatingthe device as a function of the valve switching between the first andthe second operating states.
 88. The method of claim 7 furthercomprising: applying a first command signal to the prestressedelectroactive bender actuator; moving the prestressed electroactivebender actuator through a displacement in a first direction as afunction of the first command signal; and supplying a pressurized fluidfrom the valve as a function of the prestressed electroactive benderactuator moving through the displacement in the first direction, thepressurized fluid operable to switch the device to a first state. 89.The method of claim 8 further comprising moving the valve in the firstdirection in response to the prestressed electroactive bender actuatormoving in the first direction.
 90. The method of claim 8 furthercomprising: applying a second command signal to the prestressedelectroactive bender actuator; moving the prestressed electroactivebender actuator through a displacement in a second direction as afunction of the second command signal; and terminating a supply of thepressurized fluid from the valve as a function of the prestressedelectroactive bender actuator moving through the displacement in thesecond direction, the termination of pressurized fluid operable to causethe device to switch to a second state.
 91. The method of claim 10further comprising moving the valve in the second direction in responseto the prestressed electroactive bender actuator moving in the seconddirection.
 92. A fuel injector for initiating and terminating aninjection of fuel comprising: a prestressed electroactive benderactuator operable to receive a first command signal and operable to movebetween first and second positions as a function of the command signal;an injector actuator having first and second states for respectivelyinitiating and terminating an injection of fuel from the fuel injector;and an actuator drive coupled with the prestressed electroactive benderactuator and the injection actuator, the actuator drive operable switchthe injector actuator between the first and second states as a functionof the prestressed electroactive bender actuator moving between thefirst and second positions.
 93. The apparatus of claim 1 wherein theactuator drive is adapted to be connected to a source of pressurizedfluid, the actuator drive provides a flow of a pressurized fluidrepresenting a first state in response to the prestressed electroactivebender actuator moving from the first position to the second position,and the actuator drive terminates the flow of a pressurized fluidrepresenting a second state in response to the prestressed electroactivebender actuator moving from the second position to the first position.94. The apparatus of claim 2 wherein the injector actuator initiates aninjection of fuel in response to the flow of the pressurized fluid andterminates the injection of fuel in response to an absence of the flowof the pressurized fluid.
 95. The apparatus of claim 1 wherein theactuator drive comprises: a pilot valve adapted to be connected to asource of pressurized fluid and mechanically coupled with theprestressed electroactive bender actuator, the pilot valve operable toswitch between first and second operating states as a function of theoperating states of the prestressed electroactive bender actuator; and amain valve coupled with the pilot valve, the main valve operable toswitch between first and second operating states as a function of theoperating states of the pilot valve.
 96. The apparatus of claim 4wherein in response to the first command signal, the prestressedelectroactive bender actuator moves through a displacement in a firstdirection, the pilot valve moves in the first direction, the main valvesupplies pressurized fluid to the injector actuator and the injectoractuator initiates an injection of fuel from the fuel injector.
 97. Theapparatus of claim 5 wherein in response to a second command signal, theprestressed electroactive bender actuator moves through a displacementin an opposite direction, the pilot valve moves in the oppositedirection, the main valve terminates the supply of pressurized fluid tothe injector actuator and the injector actuator terminates the injectionof fuel from the fuel injector.
 98. A method of operating a fuelinjector for initiating and terminating an injection of fuel comprising:applying a command signal to a prestressed electroactive benderactuator; switching the prestressed electroactive bender actuatorbetween first and second operating states as a function of the commandsignal; and switching an actuator drive between first and secondoperating states as a function of the prestressed electroactive benderactuator switching between the first and the second operating states,switching an injector actuator as a function of the actuator driveswitching between the first and the second operating states, therebyinitiating and terminating an injection of fuel from the fuel injector.99. A method of claim 7 further comprising: applying a first commandsignal to the prestressed electroactive bender actuator; moving theprestressed electroactive bender actuator through a displacement in afirst direction as a function of the first command signal; and supplyinga pressurized fluid to an injector actuator as a function of theprestressed electroactive bender actuator moving through thedisplacement in the first direction, the pressurized fluid operable toinitiate an injection of fuel from the fuel injector.
 100. The method ofclaim 8 further comprising: moving a pilot valve in the first directionas a function of the prestressed electroactive bender actuator movingthrough the displacement in the first direction; and opening a mainvalve to supply pressurized fluid to the injector actuator as a functionof the pilot valve moving in the first direction.
 101. The method ofclaim 9 further comprising: applying a second command signal to theprestressed electroactive bender actuator; moving the prestressedelectroactive bender actuator through a displacement in a seconddirection as a function of the second command signal; and terminating asupply of the pressurized fluid to the injector actuator as a functionof the prestressed electroactive bender actuator moving through thedisplacement in the second direction, the termination of pressurizedfluid to the injector actuator operable to terminate the injection offuel from the fuel injector.
 102. The method of claim 10 whereinterminating a supply of pressurized fluid comprises: moving the pilotvalve in the second direction as a function of the prestressedelectroactive bender actuator moving in the second direction; andclosing the main valve to terminate the supply of pressurized fluid tothe injector actuator as a function the pilot valve moving in the seconddirection.